Compare Two Table Columns Using LIKE

[Danny Rilago]

hello all - can anyone help me with comparing 2 tables to find unmatched records? I have found countless posts regarding this, but nothing has worked for me, so I'm screwing something up somewhere...

I have billing table and slas table - want to compare the value of two columns with a like clause. The billing.applcode can contain values that are like values of slas.parent_applcode, such as: billing.applcode can contain 'Q10A', 'Q10B', 'Q10C', whereas the slas.parent_applcode will only have 'Q10'


Here's what I have, but it returns all values from billing:

//FIND RECORDS IN BILLING THAT AREN'T IN SLAS//
SELECT * FROM billing
WHERE billing.applcode
NOT IN (
SELECT slas.parent_applcode
FROM slas
WHERE billing.applcode LIKE CONCAT('%', slas.parent_applcode, '%'))

Thanks in advance for your help.