[VPM] SQL statement

[Nathanael Kuipers]

Hello hello,

Hope everyone is well.  I have a quick question about what I think would be 
called a negated join but I'm not sure.  I have 2 tables:

1)blastnhsp
2)blastxhsp

Each of these tables has all the same fields, and no field in either table 
contains a null value.

What I want to do is something like the following incorrect statement:

SELECT query, qfrom, qto FROM blastnhsp WHERE NOT blastxhsp.query;

query holds an integer.  It's not serial and not designated as a primary key, 
though in essence it serves as one.  I think you get the idea of what the goal 
is here: to select records from blastnhsp that do not have corresponding 
records in blastxhsp.  What is this called?  Where should I be looking?

Thanks,

Nathanael