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Message Posted: Thu, 08 Jan 2004 @ 07:24:28 GMT
"It takes practice and knowledge to make use of explains but it's a lot better to know what plan the optimizer generated than having to guess at it"
Yes, it definetly does take a lot of practice and knowledge to use the explains - and I did just that to suggest the reordering of the joins and it was no guess work.
Given the number of rows that were present in each table and considering the joins between the 4 tables - one could simulate the problem and understand what joins would be considered in such situations. I did just that, and seeing that if it were to be a merge join that the optimizer poped up for the query then it would do a lot of good if we were to re-organize the query in a manner that would lead to less number of comparisons, especially when you had a large and small table combination.
I think there is nothing wrong in coding something explicitly (the transitive term that was derived) when you know what is in hand, rather than let the optimizer do it for you.
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