: Have a (hopefully) quick question.
: How do I UPDATE one table based on criteria in another table?
: All help will be greatly appreciated.
Depends on what you want to do.
update table1 set
column1 = (select sum(column4) from table2)
update table1 t1 set
column1 = value1
where exists (
select 1 from table2 t2
where t1.column3 = t2.column1
If you'd be more specific I might be able to give you a better example.
$ select * from users where clue > 0
no rows returned