Tag: Subquery Optimization

MySQL Subquery Optimization

Never use a subquery inside a WHERE field IN(…)  the SQL query.  It will slow down the process. Slow: SELECT * FORM table1 WHERE field1 IN (SELECT field2 FROM table2 GROUP BY field1) Instead of using a subquery inside an IN(…),  use INNER JOIN query. It will speed up the process, but in IN(…) query …

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