Re: two column int index not used correctly
Hi Ming,
In the first query, the range is known at query optimization time (you specified it as constants) and MySQL figures out that range access is the best way to read this range.
In the second query, the range is not known at query optimization time. Moreover, the range will be different for each row in table_main. MySQL cannot use range access for such queries.
Hope this helps,
Jørgen Løland
Software Engineer, MySQL, Oracle
jorgenloland.blogspot.com
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