Only records that are in the secondary query are subtracted when merging using the merge operator. For example: Bob, Jane, and Tim are in the primary query. Bob and Lisa are in the secondary query. When merging the queries using the SUB operator, Bob is removed from the merged query. The number of records in the merged query is two even though the number in the primary query (3) minus the number in the secondary query (2) would equal 1. This is because the merged query still contains both Jane and Tim.
If the record exists only in the primary query, it is included in the merged query.
If the primary and secondary queries do not have any records in common, no records are subtracted from the primary query.
When merging gift queries, it is possible for the constituent name to appear in the final query even if it is in both source queries. This is because a gift query contains gift records, not constituent records, so the gifts in the two queries may be different gifts. To confirm this, put "gift import id" in the output of each source query and check to be sure the constituent's gifts are not the same records.
To query on and eliminate constituents, recreate the queries using the constituent query type and then merge.