help with long query

[George Develekos]

I have a long query that involves a single table that has four attributes, let's call them A,B,C and T, where A/B/C are strings and T is Timestamp.

The query goes like this:

select count(*) from mytable where T between T1 and T2 and B=b and C=c and A in (select A from mytable where B=b2 and C=c2)

This query, on a InnoDB query with ~1.7million rows, on a Pentium 4 with 1G RAM, took 70min to run.

Would I benefit from a MyIsam table type? Any other suggestions?? I attempted to run this a INTERSECT operation but apparently such an operation is not supported by v4.1.

I decided to port this table from DB2 to MySQL hoping for better performance, but so far this attempt has bombed...

Thanks for any help.

George