of the sub queries of fig3 a being grouped into a parameterized sub query for example if the sub queries 304 and 306 are considered uniform with respect to each other and the sub query 308 is not considered uniform with respect to the sub queries 304 and 306 then the sub queries 304 and 306 will be grouped together and a parameterized sub query 410 generated to replace the sub queries 304 and 306 with a data object parameter 412 associated with tables 104 and 106 as shown in fig4 since sub queries that are considered to be uniform are replaced with parameterized sub query 410 query engine 112 can now optimize only a single sub query i e the parameterized sub query 410 as opposed to the multiple sub queries 304 and 306 and only generate a single access plan for parameterized sub query 410 when parameters determining which of sub queries 304 and 306 are relevant to the query results the data object parameter 412 of parameterized sub query 410 is instantiated to become functionally equivalent to sub queries 304 or 306 or both as the case may be since table 108 is not considered uniform with respect to any other sub query of the union operator and or the union all operator 302 sub query 308 is not grouped with any other sub query and consequently a separate unique access plan would need to be generated by query engine 112 for sub query 308 in determining the uniformity of sub queries of a union operator and or a union all.