Databases Demystified a self teaching guide phần 4 ppsx

... 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

... databases, including properties common to databases, prevalent database models, a brief his - tory of databases, and the rationale for focusing on the relational model. Properties of a Database A ... Logical Database Design Using Normalization 145 The Need for Normalization 147 Insert Anomaly 148 Delete Anomaly 148 Update Anomaly 148 Applying the Normalization Process 148 Choo...

Ngày tải lên: 08/08/2014, 18:22

... 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. These are most important ... relational databases were built by both IBM and UC Berkeley. e. Nearly all the commercial relational databases are descendents of either System R or INGRES. 18. Currently avai...

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... 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

... profile Composite Default screen 1 94 Databases Demystified Demystified / Databases Demystified / Oppel/ 2253 64- 9 / Chapter 7 The Data Flow Diagram The data flow diagram (DFD) is the most data centric of all the ... form relation becomes a. An index b. A referential constraint c. A table d. A view e. A database 4. The insert anomaly refers to a situation where: a. Data...

Ngày tải lên: 08/08/2014, 18:22

... several proprietary XML databases on the market. However, businesses have been reluctant to abandon relational data - bases and undergo a major paradigm shift in the way they organize and store data. So, ... 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 organ...

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... profile Composite Default screen CHAPTER 12 Databases for Online Analytical Processing 301 Demystified / Databases Demystified / Oppel/ 2253 64- 9 / Chapter 12 Data Marts A data mart is a subset of a data warehouse ... 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, foll...

Ngày tải lên: 08/08/2014, 18:22