MySQL Forums :: Performance :: LEFT JOIN with CASE WHEN

Yeah, those CASEs in the JOIN are bad news. Even this would be better, but not much:
CASE pricing.type WHEN '' THEN pricing.type LIKE '%' ELSE pricing.type = ma.type END AND
-->
(pricing.type = '' OR pricing.type = ma.type) AND

OTOH, this may be a red herring. The EXPLAIN says that it uses the 'date' index to reach into 'pricing' (pricing.date = sales.date). Once it is there, it finds about 1641 rows with the right date. Then (and only then?) it goes through the CASEs.