insert into tbl1 (value1,value2)
select value3, value4 from tbl2;
The above code inserts value3 and value4 from tbl2 INTO value1 & value2 of tbl1.
What I would like to do is add a "WHEN" statement, that first compares the two tables to make sure the combination of those two values do not exist before adding them.
EG: when tbl1.value1 & tbl1.value2 != tbl2.value3 & tbl2.value4
How would I properly write the "when" statement and incorporate it into my sample above?
(NOTE: I have added a UNIQUE property to the database so both value1 and value2 of tbl1 must be unique, but that will throw a duplicate error if the SQL is run, and nothing new gets entered if it appears later than the error)