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Re: Does DBI handle table alias?

by dragonchild (Archbishop)
on Oct 06, 2004 at 17:11 UTC ( #397097=note: print w/replies, xml ) Need Help??


in reply to Does DBI handle table alias?

The prior responses, especially VSarkiss's, are absolutely correct. You will want to verify this query from whatever commandline tools your RDBMS provides. A few thoughts on how to speed up a query:
  • Verify that you have indices on the columns you're searching on. Also, you will want to verify that the indices are being used. DBD::mysql, for example, passes all parameters in quoted, so they all look as if they are strings to MySQL. This means that comparisons to numeric columns will not use any indices, even if they are available.
  • Put your search conditions in a WHERE clause, very much like VSarkiss suggested in his update. This allows the RDBMS to optimize the query better.
  • Depending on the size of your tables and the size of the machine, some queries might just run slowly. If you're working with 1G tables and you have 256M of RAM, you're going to have issues.

Also, you might want to check the value of your webserver timeout. In Apache, the variable is called Timeout and is found in the httpd.conf. (I don't know about others, like IIS.) Some queries will simply take 1-2 minutes and if your timeout is set to 90 seconds (which isn't uncommon), you're going to have issues.

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