MySQL – Join changes starting 5.0.12

If a SQL suddenly die after an upgrade, check your query and the changes to the JOIN, especially this could cause “Unknown column ‘X.XX’ in ‘on clause’ “. The reason being before 5.0.12, the comma operator and JOIN both had the same precedence, so the join expression t1, t2 JOIN t3 was interpreted as ((t1, t2) JOIN t3). Now JOIN has higher precedence, so the expression is interpreted as (t1, (t2 JOIN t3)). Solution: specifically put the parenthesis.

Source: http://dev.mysql.com/doc/refman/5.0/en/join.html