Sams Teach Yourself SQL in 24 Hours, Third Edition By Ronald R. Plew, Ryan K. Stephens
Table of Contents
Hour 21. Working with the System Catalog
The system catalog is used only for query operationseven when being used by the database administrator. Updates to the system catalog are accomplished automatically by the database server. For example, a table is created in the database when a CREATE TABLE statement is issued by a database user . The database server then places the DDL that was used to create the table in the system catalog under the appropriate system catalog table. There is never a need to manually update any table in the system catalog. The database server for each implementation performs these updates according to actions that occur within the database, as shown in Figure 21.2.
Figure 21.2. Updates to the system catalog.
Never directly manipulate tables in the system catalog in any way (only the DBA has access to manipulate system catalog tables). Doing so may compromise the database's integrity. Remember that information concerning the structure of the database, as well as all objects in the database, is maintained in the system catalog. The system catalog is typically isolated from all other data in the database.
