DATABASE SYSTEMS (phần 15) pps

... it contains several transaction boundaries. If the database operations in a transaction do not update the database but onlyretrieve data, the transaction is called a read-only transaction. The model of a database that is used ... completes execution without error or it fails and leaves the database unchanged. 554 IChapter 17 Introduction to Transaction Processing Concepts and Theory...

Ngày tải lên: 07/07/2014, 06:20

... a relational database schema for this database application. First show all the functional dependencies that should hold among the attributes. Then design relation schemas for the database that are each in ... becomes questionable when the constraints on which they are based are hard to understand or to detect by the database designers and users who must discover these constraints. Thu...

Ngày tải lên: 07/07/2014, 06:20

... operation for a large disk file, and special techniques for external sorting are used (see Chapter 15). For a file of unordered fixed-length records using unspanned blocks and contiguous allocation, it ... block accesses to find a specific record in a file with b blocks. Ordered files are rarely used in database applications unless an additional access path, called a primary index, is use...

Ngày tải lên: 07/07/2014, 06:20

... followed and undone. 19.6 RECOVERY IN MULTIDATABASE SYSTEMS So far, we have implicitly assumed that a transaction accesses a single database. In some cases a single transaction, called a multidatabase transaction, may ... Do Not Affect the Database In general, a transaction will have actions that do not affect the database, such as generat- ing and printing messages or reports from info...

Ngày tải lên: 07/07/2014, 06:20

... attribute. )R(r 1 n 1 )R(r n )R(r =         COP 4710: Database Systems (Day 21) Page 1 Mark Llewellyn © COP 4710: Database Systems Spring 2004 Query Processing and Optimization BÀI 15, 1,5 ngày COP 4710: Database Systems Spring 2004 Query ... general database access algorithms that implement basic relational operations such as select and join. Hybrid combinations of re...

Ngày tải lên: 21/01/2014, 18:20

Ngày tải lên: 04/07/2014, 02:20

... local and remote databases and connected or disconnected interaction. Although this namespace is not discussed in detail in the book, chapter 17 pro- vides some details on using databases with ... namespace 381, 574, 681 System.XML namespace 186, 681 SystemColors class 120, 205 Control property 205 Systems. Collections namespace 461 710 INDEX Q QueryContinueDrag event 622 question mark (?...

Ngày tải lên: 07/07/2014, 04:20

Ngày tải lên: 07/07/2014, 05:20

... using, and imple- menting database systems and applications. Our presentations stresses the fundamentals of database modeling and design, the languages and facilities provided by the database management systems, and system implementation techniques. The book is meant to be used ... I Chapter 1 Databases and Database Users DATABASE SYSTEM UserS/Programmers ~ Application Programs/...

Ngày tải lên: 07/07/2014, 06:20

... are becoming quite popular. These systems provide an environment for developing database applications and include facilities that help in many facets of database systems, including database design, CUI development, querying and ... processing and optimization, their performance improved. Eventually, relational databases became the dominant type of database systems for traditiona...

Ngày tải lên: 07/07/2014, 06:20