chiprivers Posted September 25, 2010 Share Posted September 25, 2010 Other than applying a primary index to my id column, I have not used indexes in my tables before. After reading an article on top tips for mysql basics, I understand that it is best to apply an index to any column on which you will be searching on regularly. I have several tables from which I extract data from using JOINs in my queries. Do I need to apply an index to both columns used within the JOIN or just, say the right table on a LEFT JOIN? ie. table1 has a column 'table2Ref' and table 2 has column 'id'. SELECT * FROM table1 LEFT JOIN table2 ON table1.table2Ref = table2.id The id column in table2 will already have a primary index on it, but should I apply an index to the table2Ref column in table1? Quote Link to comment Share on other sites More sharing options...
fenway Posted September 25, 2010 Share Posted September 25, 2010 Only on the "right" table of any join. Quote Link to comment Share on other sites More sharing options...
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