Re: SQL Newbie needs urgently help! [optimizing query]
Hm, I wonder about MySQL's decision for the index usage. Categories, aka item_t1, is joined last and there's a condition that can use the primary key of that table.
Could you try adding "FORCE INDEX(PRIMARY)" right after "Categories item_t1"? Maybe MySQL tries to avoid reading the value for SourcePK (key_len 92 seems huge), but there are only two rows expected to be read, which should make that still perform a lot better than reading 18000 rows from Categories to perform the checks for the other conditions...
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Re: SQL Newbie needs urgently help! [optimizing query]
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