I have a strange performance issue, i think that is not possible: Given this statement:
SELECT *several_fields* FROM A, B, C WHERE *conditions* A, B are tables with several LEFT JOINS but they act as one subquery. If I execute the select above: SELECT *several_fields* FROM A, B, C WHERE *conditions* *Time: 30 secs* *Cost: 1M* If I execute the same select (same parameters) but swapping A and B in the from clause: SELECT *several_fields* FROM B, A, C WHERE *conditions* *Time: 19ms* *Cost: 10k* The plan changes dramatically: I can't see why the order of FROM clause impacts directly on the query cost and plan. If this is possible, where i can read about it? I need to know how the order of FROM clause modifies the query plan. Thanks in advance. This is my first post. Eduard Català
