Index Not Used When Joining Tables
So I have SKUMaster table that contains item details. When I created it, I put a lot of columns in an index, below is the list of my indexes
As you can see, SPU and CompanyReference is indexed in this table. Then I create a query and join SKUMaster table with another table. After I finished my query, I use EXPLAIN to see the details of my query and below is the result
Notice that possible_keys and key column is null. Is my index didn’t use by my query? What should I do to create a better query performance?
