index on datetime column

pick_up_stix

I have searched several pages of the MySQL manual, but cannot seem to find the answer to the following question:

If doing a UNIX_TIMESTAMP function on a 'datetime' column, and that column has an index - will the index be used?

[deleted]

Why would it not be used?

Sxooter

He's probably doing something like:

select * from table where function(datefield)=102938495

or something like that. I'm note sure an index on datefield would get used there.

Now, in a more robust SQL database, you could just

create index table_func_dx on table (function(datefield));

and then you'd have an index that gets used.

toma42

Originally posted by pick_up_stix
If doing a UNIX_TIMESTAMP function on a 'datetime' column, and that column has an index - will the index be used?

To find out youself, use the explain syntax:
http://www.mysql.com/doc/en/EXPLAIN.html

Explain is great anytime you're trying to optimize a query.