Unanswered: SQL problem: optimizing UNION operator
My application's search is based on some queries grouped by union operator.
My problem is that I would like to optimize the search and I cannot optimize the UNION operator.
If I add the times of all the queries I get a number infinitely small than the time obtain by the reunion or intersection of these queries.
For example, if I have:
If I add the select1, 2, 3 etc. response time I will get a very small result comparing with the union (Intersect by the use of exists) result time. I cannot use union all because I need to eliminate the duplicates.
Can you give me an advice regarding this optimizing problem?
Thanks in advanced.