Often, one of the first tasks an application performs is to display to the user a list of tables from which one or more tables are selected by the user to work with. Although the application can issue its own queries against the database system catalog to get this type of catalog information, it is best that the application calls the DB2 CLI catalog functions instead. These catalog functions provide a generic interface to issue queries and return consistent result sets across the DB2 family of servers. This allows the application to avoid server specific and release specific catalog queries.
The catalog functions operate by returning to the application a result set through a statement handle. Calling these functions is conceptually equivalent to using SQLExecDirect() to execute a select against the system catalog tables. After calling these functions, the application can fetch individual rows of the result set as it would process column data from an ordinary SQLFetch(). The DB2 CLI catalog functions are:
The result sets returned by these functions are defined in the descriptions for each catalog function. The columns are defined in a specified order. In future releases, other columns may be added to the end of each defined result set, therefore applications should be written in a way that would not be affected by such changes.
Some of the catalog functions result in execution of fairly complex queries, and for this reason should only be called when needed. It is recommended that the application save the information returned rather than making repeated calls to get the same information.