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in reply to Does DBI handle table alias?

OK - this is going to be an interesting experiment. I'm in the process of adding indeices. I'm going to add different combinations of different kinds of indices and test each one. Will keep this topic posted.

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Re^2: Does DBI handle table alias?
by The_Rabbit (Acolyte) on Oct 06, 2004 at 21:10 UTC
    Be careful... you really don't want to create anymore indexes than necessary. Even though you might see a performance increase in your test by building a bunch of extra indexes you might end up causing performance problems in other parts of the system. Remember, that whenever a rows are inserted or deleted there is an additional work that has to be for each index. Just like everything else in programming you have to strike a balance.

    Looking at the query you had problems with I am guessing that the only indexes that are going to help are to build an index for user_id and characteristic_id for both tables. Generally, columns that appear in join conditions are good candidates for building an index.