How to Optimize distinct with index

[周彦伟]

Hi,
	I have a sql : 
		Select distinct user_id from user where key1=value and
key2=value2 and key3=value2;

I add index on (key1,key2,key3,user_id), this sql use temporary table
howevery
I have thousands of queries per second.
How to optimize it?


Anthoer question:
Select * from user where user_id in(id1,id2,id3,id4,.....) order by use_id;
I add index on user_id,but after in,order use temporary table, How to
optimize it?

Thanks!

zhouyanwei