SQL Cheat Sheet
Table of Contents
Various SQL tricks and tips.
Insert, but only if not there
To insert the values ‘a’ and ‘b’ into table
foo (with columns named A, B),
but only where the values are not already there, try something like:
INSERT INTO foo ( SELECT 'a' as A, 'b' as B FROM foo WHERE A = 'a' AND B = 'b' HAVING count(*)=0 )