Re: FORCE INDEX use?

[KimSeong Loh]

You still cannot use the Event_Time index here.

Reason, is that MySQL can only use 1 index per table, and the index it selected to use is the Security_Id_idx, which is used to perform the join with table cw.

If you want to use the index, create a composite index on these 2 columns (Security_Id_idx,Event_Time), then it will reduce the "Using where" for table ev.
ev is not the first table read in this query.


In the earlier query, ev is the first table, so the WHERE condition can make use of an index to select the required rows.


Note that I do not and will not read you long query, but only extract the relevant information to show you what you could have misunderstood from you question.