Help on simple queries

[sukatoa]

Good day,

I have a table named test1 and test2 which has the same column usr and pwd
I would like to know what data in test1 that is not exist in test2

I have no idea how to query this sample to google


I tried this query

select test1.usr from test1,test2 where test1.usr != test2.usr;
(it selects all rows)

If i will try to remove test2, it doesn't recognize test2.usr ( not on scope )

May i ask what's the correct query for this?
Any reply would be appreciated

[sukatoa]

Anyways, i got it

select usr from test1 where usr not in (select usr from test2);

Can this query be optimized?

[nbiswas]

Solution to Help on simple queries

Even you can try this

select t1.usr  from test1  t1
left join (select * from test2) t2
on t1.usr = t2.usr
where t2.usr is null

Actually the above program simulates EXCEPT functionality(w hich is absent in MYSQL)

[sukatoa]

Thank you nbiswas for your reply, this helps