A persisted derived variable is simply a dynamically derived variable whose results have been permanently written into the case data.

This topic shows you how to create a persisted derived variable. The example uses the TotalInGroup dynamically derived numeric variable that we created in Dynamically derived variables.

The process of converting a dynamically derived variable into a persisted derived variable is quite simple. In DM Query, open the museum_dd_expression.mdd and museum_dd_expression.ddf files that we created in the previous topic. For step-by-step instructions, see How to run the example queries in DM Query using the museum sample, but make sure that you select museum_dd_expression.mdd and museum_dd_expression.ddf instead of museum.mdd and museum.ddf, and this time select Open Metadata Read/Write.

Type this statement in the SQL box:

This statement created a new variable in the case data called PersistedTotalInGroup. Now we need to write the results of our dynamically derived variable TotalInGroup to this new case data variable. You do that with the following statement:

We have now written the results of the dynamically derived numeric variable TotalInGroup permanently into the case data as a new persisted derived numeric variable called PersistedTotalInGroup.

Provided you selected the option to open the museum_dd_expression.mdd file in read/write mode, the UNICOM Intelligence OLE DB Provider will have created a variable called PersistedTotalInGroup in the metadata. To tidy things up you should now go back into the metadata and add a label for the variable.