Glossary

2942glp1.qxd 7/6/01 3:00 PM Page Glossary 2942glp1.qxd 7/6/01 3:00 PM Page Glossary A ACID Atomic, Consistent, Isolated, and Durable This acronym forms the definition of a transaction aggregate function A function that performs a calculation on multiple values of a specified column and returns a single value Sum, Avg, Min, and Max are examples of aggregate functions aggregate query A SQL query that summarizes information from different rows by using an aggregate function (See aggregate function) alias A substitute name for a table or column in queries Alias are used to prevent ambiguous references, to give a more descriptive name to a column in the query output or to shorten the name of a table American National Standards Institute (ANSI) An organization of American industry and business groups that develops trade and communication standards for the United States Through membership in the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC), ANSI coordinates American standards with corresponding international standards ANSI See American National Standards Institute (ANSI) atomic First characteristic of a transaction Either all of the transaction data modifications or none are performed attribute In database modeling, an attribute describes an entity For example, last name and first name are attributes of the customer entity Attributes become columns in relational databases automatic recovery Recovery process that takes place each time SQL Server is started It protects the database in case of a system failure B backup A disk, tape, or network copy of a database, transaction log, file, or filegroup A backup can be used to restore the database to a previous consistent state in case of a system failure batch A series of SQL statements executed as a group A script is made of one or many batches bigint data type An integer data type with a value from Ϫ263 (Ϫ9223372036854775808) through 263 Ϫ (9223372036854775807) binary data type A fixed-length binary data type with a maximum length of 8,000 bytes binary large object A chunk of binary data that can be large (such as images, sounds, or films stored as digital data) In SQL Server, a BLOB is stored in an image column The term BLOB may also be used to refer to large character data, such as text or ntext datatypes 2942glp1.qxd 7/6/01 3:00 PM Page Glossary bit datatype A datatype that contains a value of either or BLOB See binary large object parent record, all the related foreign keys of the child records (records having the foreign key referencing the primary key of the updated record) are deleted block A set of Transact-SQL statements enclosed by BEGIN and END char datatype A character datatype that holds a maximum of 8,000 characters Boolean An operation or expression that can be evaluated only as either true or false character set A character set defines the way SQL Server codes the characters in the char, varchar, and text datatypes Each character set is a set of 256 letters, digits, and symbols The first 128 characters are the same for all character sets; they are called ASCII characters The last 128 characters, referred to as extended characters, are unique to each character set business rules The logical rules that govern a business In SQL Server, business rules can be enforced with triggers, stored procedures, and constraints C calculated column A column that displays the result of a calculation For example, Total = UnitPrice * Quantity See Computed column CHECK constraints Defines which data values are acceptable in a column CHECK constraints are declarative integrity rules They are part of the table structure candidate key A column or a group of columns that uniquely identify each row of a table Every value of the candidate key is unique within the table One candidate key is chosen to be the primary key, while others are called alternate keys A table may contain multiple candidate keys checkpoint An event during which SQL Server writes dirty cache pages to disk A dirty page is a page that have been modified, but not yet written to disk A checkpoint writes all the pages that were dirty at the last checkpoint It occurs when a user requests it, automatically based on the amount of modification on the data, and before a clean shutdown of the server cascading delete Cascading delete can be enforced on a relationship between two tables If a user deletes a parent record, all the related child records (records having the foreign key referencing the primary key of the deleted record) are deleted cascading update Cascading update can be enforced on a relationship between two tables If a user update the primary key of a clause In Transact-SQL, a part of a SQL statement For example, a WHERE condition is called a clause of the SELECT statement clustered index One of the two types of index in SQL Server The data pages form the leaf level of the index and the records are 2942glp1.qxd 7/6/01 3:00 PM Page Glossary physically sorted on the ascending or descending order of the index key values code page See character set collation A set of rules that determines the character set used, and how data is compared, ordered, and presented column In a SQL table, a column corresponds to an attribute of the entity modeled by the table For example, the FirstName column of the Customers table stores, for every row the first name of every customer column-level collation The ability of SQL Server 2000 to support multiple collations in a single table Every character column can have its own collation (see collation) column-level constraint A constraint associated to a single column A column-level constraint is defined with the column at table creation or alteration commit An operation that saves all modifications to a database made since the beginning of a transaction The commit marks the end of a transaction and guarantees that all of the transaction’s modifications are durable composite index An index that is made of more than one column composite key A key composed of more than one column computed column A column in a table whose value is calculated at run time The values of that column are not stored in the table, but are computed based on the expression that defines the column For example: Total as UnitPrice * Quantity may be a computed column concatenation To combine two or more character (or binary) strings or expressions into a single character (or binary) string or expression concurrency A process that allows multiple users to access and change data at the same time In SQL Server, locks handle concurrency constraint A table or column property that prevents certain types of invalid data values from being stored in the table For example, a PRIMARY KEY constraint prevents inserts of duplicate values, a DEFAULT constraint stores a default value in a column if no data has been provided by the user, and a CHECK constraint forces data to comply with a specific format or with a specific range of values control-of-flow language Transact-SQL keywords that control the flow of execution of SQL statements in triggers, stored procedures, batches, and user-defined functions correlated subquery A subquery that references a column in the outer statement The inner query is executed for each candidate row in the outer statement cursor A cursor is a result set associated with a row pointer You can position the cursor on a specified row to perform any operation on that row; the most common operation being to retrieve (fetch) the row cursor datatype A special datatype used to reference a cursor 2942glp1.qxd 7/6/01 3:00 PM Page Glossary D Data Control Language (DCL) The subset of SQL statements used to control permissions on database objects DCL is formed with GRANT and REVOKE statements data definition language (DDL) The subset of SQL statements used to define all attributes and properties of a database, especially database schema, table definition, and storage strategy DDL is formed with, at least, CREATE, ALTER, and DROP statements data dictionary A group of system objects describing the database structure, permissions, users, and so on data dictionary view A system table data integrity A state in which all the data values stored in the database are correct data manipulation language (DML) The subset of SQL statements used to retrieve and manipulate data SELECT, INSERT, UPDATE, and DELETE are statements part of the DML datatype An attribute that specifies what type of information can be stored in a column, parameter, or variable A datatype can be provided by SQL Server or defined by the user database A collection of data and other objects stored, organized and presented to serve a specific purpose database catalog The set of system tables that contains the definition of all the objects in the database, as well as the definition of the database structure See data dictionary database diagram A graphical representation of the tables and relationships in a database database file One of the physical files that make up a database database object A database component: Table, index, trigger, view, key, constraint, default, rule, user-defined datatype, userdefined function or stored procedure database owner A member of the database administrator role of a database There is only one database owner The owner has full permissions in that database and determines the access and capabilities provided to other users database schema The definition of tables, primary and foreign keys of a database Also known as the database structure database script A set of SQL statements Transact-SQL scripts may be saved as files, usually ending with sql datetime data type A SQL Server system data type that stores a combined date and time value from January 1, 1753, through December 31, 9999, with an accuracy of three-hundredths of a second, or 3.33 milliseconds DBCS See double-byte character set (DBCS) DCL See Data Control Language (DCL) DDL See data definition language (DDL) deadlock A deadlock occurs when two processes own a lock on one data resource 2942glp1.qxd 7/6/01 3:00 PM Page Glossary user would wait indefinitely for the other to release the lock, the RDBMS terminates one of the processes SQL Server detects and resolves deadlock automatically deny Removes a permission from a user account and prevents the account from gaining permission through membership in groups or roles within the permission decimal datatype Fixed precision and scale numeric data from Ϫ1038 Ϫ through 1038 Ϫ dependencies The database objects that depend on other objects to be used declarative referential integrity (DRI) Definition of a relationship between two tables, being part of the table definition In TransactSQL, DRI is enforced with the FOREIGN KEY constraint default A data value, option, collation, or name assigned automatically by the system if a user does not specify the value, option, collation, or name DEFAULT constraint A property defined for a column that specifies a constant or a function to be used as the default value for the column default database The database the user is connected to immediately after logging in to SQL Server Delete query A query (SQL statement) that deletes rows from one table delimiter Characters that delimits an object name In Transact-SQL, delimiters can be either double quotation marks (“”) or brackets ([ ]) denormalize To introduce redundancy into a table Denormalization is generally introduced to enhance performance dirty pages Buffer pages that contain data modifications that have not yet been written to disk dirty read Reads that contain uncommitted data For example, userA changes a row UserB reads the changed row before userA commits the change If userA rolls back the change, userB has read a row that never logically existed distributed query A single query that accesses data from multiple data sources DML See data manipulation language (DML) double-byte character set (DBCS) A character set that uses two bytes to represent a character, allowing more than 256 characters to be represented DBCSs are typically used in environments that use ideographic writing systems, such as Japanese, Korean, and Chinese DRI See declarative referential integrity (DRI) dynamic locking The process used by SQL Server to determine the most cost-effective locks to use at any one time 2942glp1.qxd 7/6/01 3:00 PM Page Glossary E encrypted trigger A trigger that is created with a parameter that encrypts the definition text Encryption makes the information indecipherable to protect intellectual property of the developer encryption A method for keeping sensitive information confidential by changing data into an unreadable form entity An entity is a real-world object, referred to by a noun (person, place, thing, or idea), such as customers, products, books, and so on entity integrity A state in which all the rows in a table have a primary key value This ensures that there are no duplicate entries for anything represented in the table equijoin A join in which the values in the columns being joined are compared for equality, and all columns are included in the results error log A text file that records system information from SQL Server exclusive lock A lock that prevents any other transaction from acquiring a lock on a resource until the original lock on the resource is released at the end of the transaction An exclusive lock is always applied during an update operation (INSERT, UPDATE, or DELETE) explicit transaction A group of SQL statements enclosed in a transaction The transaction begins with BEGIN TRANSACTION or BEGIN DISTRIBUTED TRANSACTION, and ends with one of the following keyword: COMMIT TRANSACTION COMMIT WORK ROLLBACK TRANSACTION ROLLBACK WORK SAVE TRANSACTION expression In Transact-SQL, a combination of symbols and operators that evaluate to a single data value extended stored procedure A function in a dynamic link library (DLL) that is coded using the SQL Server 2000 Extended Stored Procedure API The function can then be invoked from Transact-SQL as if it was a Transact-SQL stored procedures Extended stored procedures can be built to perform functionality not possible with Transact-SQL stored procedures extent A group of eight contiguous pages Extents are allocated to SQL Server tables and indexes, whenever the object needs more space F fetch An operation that retrieves a row or block of rows from a cursor Transact-SQL batches, stored procedures, and triggers use the FETCH statement to fetch from TransactSQL cursors field An area in a record that stores a single data value Field is a synonym of column 2942glp1.qxd 7/6/01 3:00 PM Page Glossary file A unit of storage for a SQL Server database SQL Server uses three types of files: data files (.MDF or NDF), log files (.LDF), and backup files (.BAK) filegroup A set of one or more files that forms a unit of data allocation or of backup Filegroups are used to split data or indexes on different files or to backup set of tables/indexes independently from the database fill factor An index property that defines the amount of space on each leaf page of the index that should remain free at index creation FILLFACTOR can go from to 100, expressing the free space percentage Fill factor is used to avoid page splits and avoid performance decrease in OLTP systems fixed database role A predefined role that exists in each database The scope of the role is limited to the database in which it is defined fixed server role A predefined role that exists at the server level The scope of the role is limited to the SQL Server instance in which it is defined FK See foreign key (FK) float datatype A data type that holds floating-point number data from Ϫ1.79E ϩ 308 through 1.79E ϩ 308 Float, double precision, and float(n) are SQL Server float data types foreign key (FK) The column or combination of columns linked to the primary key (PK) or unique key in the same or another table foreign table foreign key A table that contains a forward-only cursor A cursor in which rows can be read only from the first to the last row fragmentation Occurs when data modifications are made Data or index fragmentation can be detected with DBCC SHOWCONTING statement, and data or indexes can be defragmented either by dropping and recreating clustered indexes or by using the DBCC DBREINDEX or DBCC INDEXDEFRAG statements full outer join A type of outer join in which all rows in all joined tables are included, whether they are matched or not function A piece of code that operates as a single logical unit A function is called by name, accepts optional input parameters, and returns a status and optional output parameters Transact-SQL supplies built-in functions, which cannot be modified, and supports user-defined functions, which can be created and modified by users G global variable In earlier versions of SQL Server, the term referred to the Transact-SQL system functions whose names start with two at signs (@@) grant Applies permissions to a user or to a role account Granting a permission allow that user or role to perform the action referenced by the permission 2942glp1.qxd 7/6/01 3:00 PM Page Glossary guest A special user account that can be created in a database, to allow users with SQL Server logins, but without a user account in a database to access objects and data with the permissions assigned to the guest account in that database H horizontal partitioning To split a table into smaller tables based on selected rows Each of the smaller tables has the same structure HTML See Hypertext Markup Language (HTML) Hypertext Markup Language (HTML) A tag language used to create document to be published on the World Wide Web HTML Documents include graphics and formatting tags A Web browser (such as Microsoft Internet Explorer or Netscape Navigator) is used to view these documents I identifier The name of a database object An identifier can be from through 128 characters Identifiers can be of two types: regular or delimited A delimited identifier contains forbidden characters to regular identifiers, like the space character for example identity column A column that has been defined with the identity property See identity property identity property A property that generates values that uniquely identify each row in a table When inserting rows into a table that has an identity column, SQL Server generates the next identity value automatically based on the last used identity value and the increment value specified during column creation image datatype A SQL Server variablelength binary data type with a maximum length of 231 Ϫ (2,147,483,647) bytes implicit transaction A connection option in which each SQL statement executed by the connection is considered a separate transaction, and should be committed or rolled back explicitly index In a relational database, a database object that provides fast access to table data, based on key values Indexes can also enforce uniqueness on the rows in a table SQL Server supports clustered and nonclustered indexes The primary and unique keys of a table are automatically indexed, if they are defined with constraints index page A database page containing index rows inner join An operation that retrieves rows from multiple source tables by comparing the values from columns shared between the source tables An inner join excludes rows from a source table that have no matching rows in the other source tables insensitive cursor A cursor that does not reflect data modification made to the 2942glp1.qxd 10 7/6/01 3:00 PM Page 10 Glossary underlying data by other users while the cursor is open Insert query A SQL statement that creates a new row and inserts values into specified columns, or insert rows coming from the same or another table int (integer) data type A SQL Server system data type that holds whole numbers from Ϫ231 (Ϫ2,147,483,648) through 231 Ϫ (2,147,483,647) integer In SQL Server 2000, a data type category that includes the bigint, int, smallint, and tinyint data types integrated security See Windows Authentication integrity constraint A property defined on a table or a column that prevents data inserts or updates that would create invalid data intent lock A lock placed on one level of a resource hierarchy to protect shared or exclusive locks on lower-level resources If a SQL Server process accesses a data row, and locks that row, it places intent lock at higher level (page and table level) to inform the other processes that a lock has been acquired at a lower level If another process want to exclusively lock the table containing the locked row, the intent lock places at table prevents it to acquire the exclusive lock interprocess communication (IPC) A mechanism through which operating system processes and threads exchange data and messages IPCs include local mechanisms such as Windows shared memory, or network mechanisms such as Windows Sockets IPC See interprocess communication (IPC) isolation level The property of a transaction that controls the degree to which data is isolated for use by one process and guarded against interference from other processes Setting the isolation level defines the default locking behavior for all SELECT statements in your SQL Server session J join As a verb, to combine the contents of two or more tables and produce a result set that incorporates rows and columns from each table Tables are typically joined using data that they have in common As a noun, the process or result of joining tables, as in the term “inner join” to indicate a particular method of joining tables join column The column referenced in a join condition join condition A comparison clause that specifies how tables are related by their join columns join operator A comparison operator in a join condition that determines how the two sides of the condition are evaluated and which rows are returned K key A column or group of columns that uniquely identifies a row (PRIMARY KEY or UNIQUE KEY), defines the relationship between two tables (FOREIGN KEY), or is used to build an index 2942glp1.qxd 7/6/01 3:00 PM Page 11 Glossary 11 key column A column referenced by a primary, foreign, unique, or index key key range lock A lock used to lock ranges between records in a table to prevent phantom insertions or deletions into a set of records Ensures serializable isolation level keyset-driven cursor A cursor that shows the effects of updates made to its member rows by other users while the cursor is open, but does not show the effects of inserts or deletes keyword A reserved word in SQL Server L LCID See locale identifier (LCID) leaf In a tree structure, an element that has no subordinate elements In a SQL Server index, leaf pages contains occurrences of every index keys In a clustered index, leaf pages are data pages leaf level The bottom level of a clustered or nonclustered index In a clustered index, the leaf level contains the data pages of the table In a nonclustered index, the leaf level contains data pointers (row ID or clustered key), rather than containing the data itself left outer join A type of outer join in which all rows from the left-most table in the JOIN clause are included When rows in the left table are not matched by rows in the right table, all result set columns that come from the right table are assigned a value of NULL linked server An OLE DB data source used by SQL Server 2000 distributed queries The linked server definition specifies the OLE DB provider required to access the data, and includes enough addressing information for the OLE DB provider to connect to the data livelock A request for an exclusive lock that is repeatedly denied because a series of overlapping shared locks keeps interfering SQL Server detects the situation after four denials and refuses further shared locks local variable A user-defined variable that has an assigned value A local variable is defined with a DECLARE statement, assigned an initial value with a SELECT or SET statement, and used within the statement batch or procedure in which it was declared locale The Windows operating-system attribute that defines certain behaviors related to language The locale defines the code page, or character set, used to store character data, and the order in which characters are sorted It also defines languagespecific items such as the format used for dates and time and the character used to separate decimals in numbers Each locale is identified by a unique number, called a locale identifier or LCID SQL Server 2000 collations are similar to locales locale identifier (LCID) A number that identifies a Windows-based locale lock A system object placed by SQL Server on a resource, to restrict access in a multiuser environment SQL Server locks rows, pages, extents, tables, and files 2942glp1.qxd 12 7/6/01 3:00 PM Page 12 Glossary lock escalation The process of converting many fine-grain locks into fewer coarse-grain locks, thereby reducing system overhead, but increasing system contention log file A file containing the transaction log of a database See transaction log logical name A name used to identify a data or log file A logical name for a file must correspond to the rules for identifiers, with no more than 30 characters logical operators The operators AND, OR, and NOT Used to connect search conditions in WHERE clauses login (account) An identifier that gives a user permission to connect to SQL Server 2000 using SQL Server Authentication Users connecting to SQL Server 2000 using Windows NT Authentication are identified by their Windows 2000 login, and not need a separate SQL Server 2000 login login security mode A security mode that determines the manner in which a SQL Server 2000 instance validates a login request There are two types of login security: Windows Authentication and SQL Server authentication M Make Table query A SQL statement that creates a new table and copy new rows from another table This query is executed with the SELECT INTO statement many-to-many relationship A relationship between two tables in which rows in each table have multiple matching rows in the related table Many-to-many relationships are resolved and implemented by using a third table called a junction table and adding the primary key columns from each of the other two tables to this table many-to-one relationship A relationship between two tables in which one row in one table can relate to many rows in another table master database The database that controls a SQL Server instance It stores and manages user accounts, active processes, server-wide variables, system error messages, tapes, and disks available on the system, and active locks meta data Information about the properties of data, such as the type of data in a column (numeric, text, and so on) or the length of a column Mixed Mode Combines Windows Authentication and SQL Server Authentication Mixed Mode allows users to connect to an instance of SQL Server, through either a Windows NT 4.0/2000 user account or a SQL Server login model database A database installed with SQL Server that provides the template for new user databases Each time you create a new database, SQL Server 2000 copies in the contents of the model database money datatype A SQL Server system data type that stores monetary values from Ϫ263 (Ϫ922,337,203,685,477.5808) through 263 Ϫ (ϩ922,337,203,685,477.5807), with accuracy to a ten-thousandth of a monetary unit 2942glp1.qxd 7/6/01 3:00 PM Page 13 Glossary 13 N nchar datatype A fixed-length Unicode data type with a maximum of 4,000 characters Unicode characters use bytes per character and support all international characters nested query A SELECT statement that contains one or more subqueries See subquery Net-Library A SQL Server communications component that isolates the SQL Server client software and database engine from the network APIs The SQL Server client software and database engine send generic network requests to a Net-Library, which translates the request to the specific network commands of the protocol chosen by the user niladic functions Functions that have no input parameters nonclustered index An index in which the logical order of the index is different than the physical, stored order of the rows on disk nonleaf In a tree structure, an element that has one or more subordinate elements In an index, a non-leaf level node points to another non-leaf level node or to a leaf level node nonrepeatable read A non-repeatable read occurs when a transaction read a data once, then a second time, but an update occurred between these two reads Non-repeatable reads are normal with default isolation level normalization rules A set of database design rules that eliminates data redundancy, by defining keys and creating new relationships and new entities ntext datatype A variable-length Unicode data type that can hold a maximum of 230 Ϫ (1,073,741,823) characters ntext columns store a 16-byte pointer in the data row, and the data is stored separately NULL An entry that has no explicitly assigned value NULL is not equivalent to zero or blank NULL is equivalent to unknown Therefore, NULL is not greater or less than, or equal to any other value nullability The property of a column, parameter, or variable that specifies whether it allows null data values numeric expression Any expression that evaluates to a number The expression can be any combination of variables, constants, functions, and operators nvarchar data type A variable-length Unicode datatype with a maximum of 4,000 characters O object One of the components of a database: a table, index, trigger, view, key, constraint, default, rule, user-defined datatype, or stored procedure object owner The security account that controls the permissions for an object, usually the creator of the object object permission An attribute that controls the ability to perform operations on an object For example, table permissions control which users can execute SELECT, INSERT, 2942glp1.qxd 14 7/6/01 3:00 PM Page 14 Glossary UPDATE, and DELETE, statements against the table OLE DB A COM-based application programming interface (API) for accessing data OLE DB supports accessing data stored in any format (databases, spreadsheets, text files, and so on) for which an OLE DB provider is available OLE DB provider A software component that exposes OLE DB interfaces Each OLE DB provider exposes data from a particular type of data source (for example SQL Server databases, Access databases, or Excel spreadsheets) OLTP See online transaction processing (OLTP) one-to-many relationship See many-toone relationship one-to-one relationship A relationship between two tables in which a single row in the first table can be related only to one row in the second table, and a row in the second table can be related only to one row in the first table online redo log Synonym for transaction log See transaction log online transaction processing (OLTP) A data processing system designed to record all of the business transactions of an organization as they occur An OLTP system is characterized by many concurrent users actively inserting, updating, and deleting data optimizer See query optimizer outer join A join that includes all the rows from the joined tables that have met the search conditions, even rows from one table for which there is no matching row in the other join table For result set rows returned when a row in one table is not matched by a row from the other table, a value of NULL is supplied for all result set columns that are resolved to the table that had the missing row P page An contiguous 8KB of data SQL Server allocates database space in pages Pages can mainly contain table or index data Some pages are reserved for system data page split The process of moving half the rows in a full data or index page to two new pages to make room for a new row or index entry phantom The insertion of a new row or the deletion of an existing row in a range of rows previously read by another process that has not yet committed its transaction The process with the uncommitted transaction cannot repeat its original read because of the change to the number of rows in the range SQL Server uses key-range locking to prevent phantoms, with a serializable isolation level See key-range locking physical read A request to move data from the disk to the data cache When a query needs to access data, it requests logical reads (in-memory reads) If the data is not in memory, SQL Server needs to access to the disk to read data The number of physical reads is less or equal to the number of logical reads 2942glp1.qxd 7/6/01 3:00 PM Page 15 Glossary 15 PK See primary key (PK) positioned update An update, insert, or delete operation performed on a row at the current position of the cursor The actual change is made in the rows of the base tables used to build the current row in the cursor Transact-SQL batches, stored procedures, and triggers use the WHERE CURRENT OF clause to perform positioned updates precision The maximum total number of decimal digits that can be stored, both to the left and right of the decimal point primary key (PK) A column or set of columns that uniquely identify all the rows in a table Primary keys not allow null values procedure cache The part of the SQL Server memory pool that is used to store execution plans for Transact-SQL batches, stored procedures, and triggers Execution plans record the steps that SQL Server must take to produce the results specified by the Transact-SQL statements contained in the batches, stored procedures, or triggers Process An operation executed by an active connection pubs database A sample database provided with SQL Server Q query optimizer The SQL Server database engine component responsible for generating optimized execution plans for SQL statements R range query A query that specifies a range of values as part of the search criteria, such as all rows from through 50 RDBMS See relational database management system (RDBMS) real datatype A SQL Server system data type that has 7-digit precision Floating precision number data from Ϫ3.40E ϩ 38 through 3.40E ϩ 38 Storage size is bytes record A group of related fields (columns) of information treated as a unit A record is synonymous to row recovery interval The maximum amount of time that the database engine should require to recover a database The database engine ensures that the active portion of the database log is small enough to recover the database in the amount of time specified for the recovery interval redo log file Synonym for backup file See backup file referential integrity (RI) A rule stating that a child instance cannot exist if there is no corresponding parent instance reflexive relationship A relationship from a column or combination of columns in a table to other columns in that same table relational database A collection of information organized in tables 2942glp1.qxd 16 7/6/01 3:00 PM Page 16 Glossary relational database management system (RDBMS) A system that organizes data into related rows and columns and provides mechanisms to access and update this data SQL Server is a relational database management system (RDBMS) horizontal line in the table Each row in the table represents a single occurrence of the object modeled by the table and stores the values for all the attributes of that object relationship A link between tables that references the primary key in one table to a foreign key in another table rule A database object that is bound to columns or user-defined datatypes, and specifies which data values are acceptable in a column CHECK constraints provide the same functionality and are preferred because they are in the SQL-92 standard replication A process that distributes data and objects from one database to another and then synchronizes information between databases based on a schedule result set The set of rows returned from a SELECT statement revoke Removes a previously granted or denied permission from a user account, role, or group in the current database right outer join A type of outer join in which all rows in the right-most table in the JOIN clause are included When rows in the right table are not matched in the left table, all result set columns that come from the left table are assigned a value of NULL roll back To undo the updates performed by one or more partially completed transactions row lock A lock on a row in a table S savepoint A marker that allows an application to roll back part of a transaction The application must still commit or roll back the full transaction when it is complete scalar aggregate An aggregate function, such as MIN(), MAX(), or AVG(), that is specified in a SELECT statement column list that contains only aggregate functions When the column list contains only aggregate functions, then the result set has only one row giving the aggregate values calculated from the source rows that match the WHERE clause predicates roll forward To apply all the completed transactions from a database or log backup in order to recover a database to a point in time or the point of failure schema In the SQL-92 standard, a collection of database objects that are owned by a single user and form a single namespace In Transact-SQL, much of the functionality associated with schemas is implemented by database user IDs row An instance of an entity In an SQL table, the collection of elements that form a script A collection of Transact-SQL statements used to perform an operation 2942glp1.qxd 7/6/01 3:00 PM Page 17 Glossary 17 Transact-SQL scripts are stored as files, usually with the sql extension scroll The ability to move around a cursor in directions other than forward-only Users can move up and down the cursor search condition In a WHERE or HAVING clause, predicates that specify the conditions that the source rows must meet to be included in the SQL statement SELECT The Transact-SQL statement used to retrieve data from one or more tables, and to return this data to an application or another Transact-SQL statement, or to populate a cursor select list The SELECT statement clause that defines the columns of the result set returned by the statement The select list is a commaseparated list of expressions, such as column names, functions, or constants self join A join in which records from a table are combined with other records from the same table when there are matching values in the joined fields A self join can be an inner join or an outer join In database diagrams, a self join is called a reflexive relationship sensitive cursor A cursor that can reflect data modifications made to underlying data by other users while the cursor is open serializable The highest transaction isolation level Serializable transactions lock all rows they read or modify, and keep these locks until the end of the transaction, to ensure the transaction is completely isolated from other tasks server cursor A cursor implemented on the server Only the rows fetched are sent to the client severity level A number indicating the relative significance of an error generated by the SQL Server database engine Values range from informational (1) to severe (25) shared lock A lock placed by a read operation Other users can read the data concurrently, but no transaction can acquire an exclusive lock on the data until all the shared locks have been released Showplan A report showing the execution plan for an SQL statement The SET SHOWPLAN_TEXT and SET SHOWPLAN_ALL statements produce textual showplan output SQL Query Analyzer and SQL Server Enterprise Manager can display showplan information as a graphical tree smalldatetime datatype Date and time data from January 1, 1900, through June 6, 2079, with an accuracy of one minute smallint datatype SQL Server system integer data from Ϫ215 (Ϫ32,768) through 215 Ϫ (32,767) smallmoney datatype A SQL Server system data type that stores monetary values from Ϫ214,748.3648 through ϩ214,748.3647, with accuracy to a tenthousandth of a monetary unit Storage size is bytes When smallmoney values are displayed, they are rounded up two places sort order The set of rules in a collation that define how characters are evaluated in 2942glp1.qxd 18 7/6/01 3:00 PM Page 18 Glossary comparison operations and the sequence in which they are sorted SQL See Structured Query Language (SQL) SQL collation A set of SQL Server 2000 collations whose characteristics match those of commonly-used code page and sort order combinations from earlier versions of SQL Server SQL collations are compatibility features that let sites choose collations that match the behavior of their earlier systems SQL Mail A component of SQL Server that allows SQL Server to send and receive mail messages through the built-in Windows NT or Windows 2000 Messaging Application Programming Interface (MAPI) SQL query An SQL statement, such as SELECT, INSERT, UPDATE, DELETE, or CREATE TABLE SQL Server Authentication One of two mechanisms for validating connections to SQL Server Users must specify a SQL Server login ID and password when they connect The SQL Server instance ensures the login ID and password combination are valid before allowing the connection to succeed SQL statement An SQL or Transact-SQL command, such as SELECT or DELETE, that performs some action on data SQL-92 The version of the SQL standard published in 1992 The international standard is ISO/IEC 9075:1992 Database Language SQL The American National Standards Institute (ANSI) also published a corresponding standard (Data Language SQL X3.135-1192), so SQL-92 is sometimes referred to as ANSI SQL in the United States sql variant datatype Data type that stores values of various SQL Server-supported data types except text, ntext, timestamp, and sql_variant standard security See SQL Server Authentication statement permission A type of permission that controls that controls whether a user can execute CREATE or BACKUP statements static cursor A cursor that shows the result set exactly as it was at the time the cursor was opened Static cursors not reflect updates, deletes, or inserts made to underlying data while the cursor is open It is a synonym to snapshot cursor stored procedure A precompiled collection of Transact-SQL statements stored under a name and processed as a unit SQL Serversupplied stored procedures are called system stored procedures string A set of contiguous bytes that contain a single character-based or binary data value In character strings, each byte, or pair of bytes, represents a single alphabetic letter, special character, or number In binary strings, the entire value is considered to be a single stream of bits that not have any inherent pattern string functions Functions that perform operations on character or binary strings Built-in string functions return values com- 2942glp1.qxd 7/6/01 3:00 PM Page 19 Glossary 19 monly needed for operations on character data Structured Query Language (SQL) A language used to insert, retrieve, modify, and delete data in a relational database SQL also contains statements for defining and administering the objects in a database SQL is the language supported by most relational databases, and is the subject of standards published by the International Standards Organization (ISO) and the American National Standards Institute (ANSI) SQL Server 2000 uses a version of the SQL language called Transact-SQL subquery A SELECT statement nested inside another SELECT, INSERT, UPDATE, or DELETE statement, or inside another subquery sysname A system-supplied user-defined data type that is a synonym for nvarchar(128) and is used to reference database object names system administrator The person or group of people responsible for managing an instance of SQL Server System administrators have full permissions to perform all actions in an instance of SQL Server System administrators are either members of the sysadmin fixed server role, or log in using the sa login ID system catalog A set of system tables that describe all the characteristics of an instance of SQL Server The system catalog records meta data such as the definitions of all users, all databases, all objects in each database, and system configuration information such as server and database option settings system databases A set of four databases present in all instances of SQL Server that are used to store system information: • The Master database stores all instancelevel meta data, and records the location of all other databases • The Tempdb database stores objects that only exist for the length of a single statement or connection, such as temporary tables or stored procedures • The Model database is used as a template for creating all user databases • The Msdb database is used by the SQL Server Agent to record information on jobs, alerts, and backup histories system functions A set of built-in functions that perform operations on and return the information about values, objects, and settings in SQL Server system stored procedures A set of SQL Server-supplied stored procedures that can be used for actions such as retrieving information from the system catalog or performing administration tasks system tables Built-in tables that form the system catalog for SQL Server T table A two-dimensional object, consisting of rows and columns, used to store data in a relational database Each table stores information about one of the types of objects modeled by the database The columns of a 2942glp1.qxd 20 7/6/01 3:00 PM Page 20 Glossary table represent an attribute of the modeled object Each row represents one occurrence of the instance tinyint datatype A SQL Server system data type that holds whole numbers from through 255 Its storage size is byte table datatype A special datatype used to store a result set for later processing Transact-SQL Transact-SQL is an extension of the ANSI SQL language defined by the International Standards Organization (ISO) and the American National Standards Institute (ANSI) Specific to SQL Server, it goes beyond the standard and defines keywords dedicated to the SQL Server environment table lock A lock on a table table scan A data retrieval operation where the database engine must read all the pages in a table to find the rows that qualify for a query table-level constraint A constraint based on one or more columns, and defined at the end of the CREATE TABLE statement tabular data stream (TDS) The SQL Server internal client/server data transfer protocol TDS allows client and server products to communicate regardless of operatingsystem platform, server release, or network transport Tempdb database The database that provides a storage area for temporary tables, temporary stored procedures, and other temporary working storage needs text datatype A SQL Server system datatype that specifies variable-length nonUnicode data with a maximum length of 231 Ϫ1 (2,147,483,647) characters The text datatype cannot be used for variables or parameters in stored procedures timestamp data type A SQL Server system datatype that is a monotomically increasing counter whose values are always unique within a database transaction A group of database operations combined into a logical unit of work that is either wholly committed or rolled back A transaction is defined by the ACID acronym: Atomic, Consistent, Isolated, and Durable transaction log A database file in which all changes to the database are recorded In case of failure, SQL Server reads the transaction logs to recover the databases trigger A particular type of stored procedure that executes automatically when data in a specified table is inserted, updated, or deleted Triggers are often created to enforce referential integrity or consistency among logically related data in different tables trusted connection A Windows network connection that can be opened only by users who have been authenticated by the network The users are identified by their Windows login ID and not have to enter a separate SQL Server login ID tuple A synonym of record See record 2942glp1.qxd 7/6/01 3:00 PM Page 21 Glossary 21 two-phase commit A process that ensures transactions that apply to more than one server are completed on all servers or on none U Unicode Unicode defines a set of 65,536 letters, numbers, and symbols that SQL Server recognizes in the nchar, nvarchar, and ntext datatypes It is related to but separate from character sets Unicode characters are double-byte Unicode collation This acts as a sort order for Unicode data It is a set of rules that determines how SQL Server compares, collates, and presents Unicode data in response to database queries Union query A query that combines two tables by appending one table onto the other UNIQUE constraints Constraints that enforce entity integrity on a non-primary key A unique index is created automatically to enforce uniqueness of data unique index An index prohibiting duplicate index or key values The system checks for duplicate key values when the index is created and checks each time data is added with an INSERT or UPDATE statement uniqueidentifier datatype A datatype containing a unique identification number stored as a 16-byte binary string used for storing a globally unique identifier (GUID) update The act of modifying one or more data values in an existing row or rows, typi- cally by using the UPDATE statement Sometimes, the term update refers to any data modification, including insert, update, and delete operations update lock A lock placed on resources (such as row, page, table) that can be updated Updated locks are used to prevent a common form of deadlock, called transforming deadlock, that occurs when two or more processes are locking resources to potentially update them later Update query A query that changes the values in columns of one or more rows in a table update statistics A process that recalculates the distribution of key values in specified indexes These statistics are used by the query optimizer to determine the most efficient way to execute a query user (account) A SQL Server security account that represents a specific user in a database Each user’s Windows account or SQL Server login is mapped to a user account in a database Then, the appropriate permissions are granted to the user account Each user account can only access data with which it has been granted permission to work user-defined datatype A datatype, based on a system datatype, created by the user Rules and defaults can be bound to userdefined datatypes user-defined function A Transact-SQL function defined by a user Functions encapsulate frequently performed logic in a named 2942glp1.qxd 22 7/6/01 3:00 PM Page 22 Glossary entity that can be called by Transact-SQL statements instead of recoding the logic in each statement V varbinary datatype A SQL Server system datatype that holds up to 8,000 bytes of variable-length binary data varchar data type A SQL Server system data type that holds variable-length nonUnicode data with a maximum of 8,000 characters variables See local variable vertical partitioning To segment a single table into multiple tables based on selected columns Each of the multiple tables has the same number of rows but fewer columns view A pseudo-table A database object that can be referenced the same way as a table in SQL statements Views are named SELECT statement W WHERE clause The part of an SQL statement that specifies which records to retrieve wildcard characters Characters, including underscore (_), percent (%), and brackets ([ ]), used with the LIKE keyword for pattern matching Windows Authentication One of two mechanisms for validating attempts to connect to SQL Server Users are identified by their Windows user or group when they connect Windows collation A set of rules that determines how SQL Server sorts character data It is specified by name in the Windows Control Panel and in SQL Server 2000 during setup write-ahead log A transaction logging method in which the log is always written prior to the data [...]...2942glp1.qxd 7/6/01 3:00 PM Page 11 Glossary 11 key column A column referenced by a primary, foreign, unique, or index key key range lock A lock used to lock ranges between records in a table to prevent phantom insertions or deletions into... lock A system object placed by SQL Server on a resource, to restrict access in a multiuser environment SQL Server locks rows, pages, extents, tables, and files 2942glp1.qxd 12 7/6/01 3:00 PM Page 12 Glossary lock escalation The process of converting many fine-grain locks into fewer coarse-grain locks, thereby reducing system overhead, but increasing system contention log file A file containing the... that stores monetary values from Ϫ263 (Ϫ922,337,203,685,477.5808) through 263 Ϫ 1 (ϩ922,337,203,685,477.5807), with accuracy to a ten-thousandth of a monetary unit 2942glp1.qxd 7/6/01 3:00 PM Page 13 Glossary 13 N nchar datatype A fixed-length Unicode data type with a maximum of 4,000 characters Unicode characters use 2 bytes per character and support all international characters nested query A SELECT... permission An attribute that controls the ability to perform operations on an object For example, table permissions control which users can execute SELECT, INSERT, 2942glp1.qxd 14 7/6/01 3:00 PM Page 14 Glossary UPDATE, and DELETE, statements against the table OLE DB A COM-based application programming interface (API) for accessing data OLE DB supports accessing data stored in any format (databases, spreadsheets,... reads) If the data is not in memory, SQL Server needs to access to the disk to read data The number of physical reads is less or equal to the number of logical reads 2942glp1.qxd 7/6/01 3:00 PM Page 15 Glossary 15 PK See primary key (PK) positioned update An update, insert, or delete operation performed on a row at the current position of the cursor The actual change is made in the rows of the base tables... relationship from a column or combination of columns in a table to other columns in that same table relational database A collection of information organized in tables 2942glp1.qxd 16 7/6/01 3:00 PM Page 16 Glossary relational database management system (RDBMS) A system that organizes data into related rows and columns and provides mechanisms to access and update this data SQL Server is a relational database... IDs row An instance of an entity In an SQL table, the collection of elements that form a script A collection of Transact-SQL statements used to perform an operation 2942glp1.qxd 7/6/01 3:00 PM Page 17 Glossary 17 Transact-SQL scripts are stored as files, usually with the sql extension scroll The ability to move around a cursor in directions other than forward-only Users can move up and down the cursor... bytes When smallmoney values are displayed, they are rounded up two places sort order The set of rules in a collation that define how characters are evaluated in 2942glp1.qxd 18 7/6/01 3:00 PM Page 18 Glossary comparison operations and the sequence in which they are sorted SQL See Structured Query Language (SQL) SQL collation A set of SQL Server 2000 collations whose characteristics match those of commonly-used... that do not have any inherent pattern string functions Functions that perform operations on character or binary strings Built-in string functions return values com- 2942glp1.qxd 7/6/01 3:00 PM Page 19 Glossary 19 monly needed for operations on character data Structured Query Language (SQL) A language used to insert, retrieve, modify, and delete data in a relational database SQL also contains statements... and columns, used to store data in a relational database Each table stores information about one of the types of objects modeled by the database The columns of a 2942glp1.qxd 20 7/6/01 3:00 PM Page 20 Glossary table represent an attribute of the modeled object Each row represents one occurrence of the instance tinyint datatype A SQL Server system data type that holds whole numbers from 0 through 255 ...2942glp1.qxd 7/6/01 3:00 PM Page Glossary A ACID Atomic, Consistent, Isolated, and Durable This acronym forms the definition of a... refer to large character data, such as text or ntext datatypes 2942glp1.qxd 7/6/01 3:00 PM Page Glossary bit datatype A datatype that contains a value of either or BLOB See binary large object... data pages form the leaf level of the index and the records are 2942glp1.qxd 7/6/01 3:00 PM Page Glossary physically sorted on the ascending or descending order of the index key values code page