Databases Demystified a self teaching guide phần 7 docx

... considered a best practice because it can lead to a lack of data sharing. Moreover, placing geographic or organizational unit names in table names plays havoc every time the organization changes. CHAPTER ... synchronizing data updates for any redundantly stored data • More expensive than the centralized model • Lack of guidelines and best practices for how to partition data and applicatio...

Ngày tải lên: 08/08/2014, 18:22

... contains more data than a data warehouse. e. The project has a lower overall cost than a data warehouse project. 16. Building a data warehouse first, followed by data marts: a. Will delay data mart ... screen CHAPTER 12 Databases for Online Analytical Processing 301 Demystified / Databases Demystified / Oppel/ 225364-9 / Chapter 12 Data Marts A data mart is a subset of a...

Ngày tải lên: 08/08/2014, 18:22

... models, a brief his - tory of databases, and the rationale for focusing on the relational model. Properties of a Database A database is a collection of interrelated data items that are managed as a ... database can be defined as the file that contains the data items. Oracle Corporation defines their database as a collec - tion of physical files that are managed by an instance of...

Ngày tải lên: 08/08/2014, 18:22

... commonly appear in data flow diagrams as a source or destination of data. These diagrams are discussed in Chapter 7. Attributes An attribute is a unit fact that characterizes or describes an entity ... screen Constraints A constraint is a rule placed on a database object (typically a table or column) that restricts the allowable data values for that database object in some way....

Ngày tải lên: 08/08/2014, 18:22

... row are called aggregate functions. The following table shows aggregate functions that are commonly used in relational databases: Function Name Description AVG Calculates the average value for a ... one-to-many, one-to-one, or many-to-many 5. The Microsoft Access Show Table dialog box: a. Lists all tables in the database and allows for the metadata about tables to be added, changed, and...

Ngày tải lên: 08/08/2014, 18:22

... that ends every SQL statement. In Oracle, a transaction is automatically started for each database user session as soon as the user connects to the database. At any time, the database user can ... table’s data. The ALTER TABLE Statement The ALTER TABLE statement may be used to change many aspects of the definition of a database table. Again, there is a wide variation in implementation a...

Ngày tải lên: 08/08/2014, 18:22

... in tables • Storing summarized data in tables Note also that normalization is intended to remove anomalies from databases that are used for online transaction-processing systems. Databases that ... historical data used solely for analytical purposes are not as subject to insert, update, and de - lete anomalies. Chapter 12 contains more information on databases that hold histori - cal in...

Ngày tải lên: 08/08/2014, 18:22

... profile Composite Default screen 194 Databases Demystified Demystified / Databases Demystified / Oppel/ 225364-9 / Chapter 7 The Data Flow Diagram The data flow diagram (DFD) is the most data centric of all the ... normalization is a. To eliminate redundant data b. To remove certain anomalies from the relations c. To provide a reason to denormalize the database d. To optimize dat...

Ngày tải lên: 08/08/2014, 18:22

... even to a different version of the same vendor’s database). Connecting Databases to Java Applications Java started as a proprietary programming language (originally named Oak) that was developed ... that binds the API to the particular database and platform, and a definition known as the ODBC data source contains the information necessary for a particular application to connect with...

Ngày tải lên: 08/08/2014, 18:22

... 62. a, b, d 63. c 64. b, d, e 65. a, c, e 66. a, d 67. c, d, e 68. a, c, e 69. a, e 70 . a, b, d, e 71 . a, c, d 72 . b, d 73 . c, d 74 . a, b 75 . a, c, e 76 . b, c, d 77 . a, b, c, e 78 . a, b, d, e 79 . ... Atomicity d. Autonomous e. Analog 82. Database locks: a. Are implemented in exactly the same way by all major database vendors b. Are controls placed by the DBMS t...

Ngày tải lên: 08/08/2014, 18:22