OLAP_CONDITION Overview

OLAP_CONDITION modifies an analytic workspace within the context of a SELECT FROM OLAP_TABLE statement. You can specify OLAP_CONDITION like other Oracle functions, typically in the WHERE clause.

You can use OLAP_CONDITION to set an option, execute a LIMIT command, execute an OLAP model or forecast, or run a program. The changes made to the workspace can be transitory or they can persist in your session upon completion of the query.

Entry Points in the Limit Map

Parameters of OLAP_CONDITION identify an invocation of OLAP_TABLE, specify an entry point in the limit map, and provide the OLAP DML command to be executed at that entry point.

The target limit map must include a ROW2CELL column. OLAP_CONDITION uses this column to identify an instance of OLAP_TABLE. Within that instance OLAP_CONDITION executes the OLAP DML command at one of three possible entry points. The entry point that you specify will determine whether the condition affects the data returned by the query and whether the condition remains in effect upon completion of the query.

OLAP_CONDITION can be triggered at any of the following points:

Before the status of the dimensions in the limit map is saved (which occurs before the result set is calculated).
After the result set has been calculated and before it is fetched. (Default)
After the result set has been fetched and the status of the dimensions in the limit map has been restored.

The entry points are described in detail in Table 6-2, "Entry Points for OLAP_CONDITION in the OLAP_TABLE Limit Map".

Dynamically Modifying a Workspace during a Query

There are several mechanisms for modifying an analytic workspace on the fly during the execution of OLAP_TABLE. In addition to OLAP_CONDITION, you can use syntax supported by the OLAP_TABLE function itself: The PREDMLCMD and POSTDMLCMD clauses in the limit map, as well as the olap_command parameter. OLAP_CONDITION has the advantage of portability, since it is not embedded within OLAP_TABLE, and versatility, since it can be applied at different entry points.

OLAP_TABLE saves the status of dimensions in the limit map before executing the LIMIT commands that generate the result set for the query. After the data is fetched, OLAP_TABLE restores the status of the dimensions. You can specify a PREDMLCMD clause in the limit map to cause an OLAP DML command to execute before the dimension status is saved. Modifications resulting from the PREDMLCMD clause remain in the workspace after execution of OLAP_TABLE, unless reversed with a POSTDMLCMD clause. For more information, see "Limit Map Parameter".

The olap_command parameter of OLAP_TABLE specifies an OLAP DML command that executes immediately before the result set is fetched. In some circumstances, the olap_command parameter may contain an OLAP DML FETCH command, which itself manages the fetch. Limits set by the olap_command parameter are only in effect during the execution of OLAP_TABLE. For more information, see "OLAP Command Parameter".