indexes

[chiprivers]

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?

[fenway]

Only on the "right" table of any join.