Re: Many Table Scanned instead of One table.
Read the mysql manual about optimizer - or these excelent articles:
http://hackmysql.com/documents
It does not matter which table is read first - result will be the same. Mysql tries to choose the order based on its estimation of how optimal it would be. It may be faster to get 1000 rows from index than to table-scan 50 rows. If you use indexes and think the decision mysql has made is not correct, try to OPTIMIZE TABLE, which would update the index "statistics" - the metrics on which the calculation are based (it can become outdated when there are many changes to the table).
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February 15, 2008 10:36AM
Re: Many Table Scanned instead of One table.
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March 12, 2008 09:37AM
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