What does the data dictionary include?

Content: 1. Information about all schema objects in the database, such as tables, views, clusters, and indexes; 2. How much space is allocated, how much space is currently used, etc.; 3. Default values ​​of columns; 4 , Constrain the integrity of the information; 5. The name of the user; 6. The permissions granted to the user and role; 7. Audit information of the user's access or use; 8. Other generated database information.

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

Data dictionary refers to the definition and description of data items, data structures, data flows, data storage, processing logic, etc. Its purpose is to provide a detailed explanation of each element in the data flow diagram. Use data dictionaries for simple modeling projects. Simply put, a data dictionary is a collection of information that describes data and is a collection of definitions of all data elements used in the system.

The data dictionary is a directory that records database and application metadata that users can access. Active data dictionary refers to a data dictionary whose contents can be automatically updated by the DBMS when the database or application structure is modified. A passive data dictionary is a data dictionary whose contents must be updated manually when modified.

Composition of data dictionary:

1, data items

2, data structure

3, data flow

4. Data storage

5. Processing process

6. External entities

Contents included in the data dictionary

The data dictionary is an important part of the database. It stores relevant information used by the database and is a set of read-only tables for users. The content of the data dictionary includes:

1. Information about all schema objects in the database, such as tables, views, clusters, and indexes.

2. How much space is allocated, how much space is currently used, etc.

3. The default value of the column.

4. Constraint information integrity.

5. User’s name.

6. Permissions granted to users and roles.

7. Audit information of user access or use.

8. Other generated database information.

The database data dictionary is a set of table and view structures. They are stored in the SYSTEM table space.

The database data dictionary is not only the center of every database. And it is also very important information for every user. Users can access the database data dictionary using SQL statements.

A collection of information about data is a directory that users can access to record database and application metadata. It is a physical and logical description of the table information in the database.

For more related knowledge, please visit the FAQ column!

The above is the detailed content of What does the data dictionary include?. For more information, please follow other related articles on the PHP Chinese website!