AVERAGE

Returns the arithmetic mean of all the values in a given field on a child table.

AVERAGE ( <field_name> [, <filter_query>] )

field_name: The numeric field for which to calculate the average.
filter_query: A query string defining the records to include in the calculation.

Example: create a field on the CUSTOMER table to return the average price that each customer paid for a product with a product code of B.

AVERAGE( [PRODUCT.PRODUCT_VALUE],[PRODUCT.PRODUCT_CODE] = "B" )