MySQL 1054错误 Unknown column .... in 'on clause'

[Err] 1054 - Unknown column 'o.ordersId' in 'on clause'

解决方法：将from后面的表用()来。

例：

SELECT a.id, b.id, c.id FROM A a, B b LEFT JOIN C c ON c.a_id = a.a_id AND c.b_id = b.b_id  

这句话在mysql5下执行会有问题，要把联合的表用括号包含起来才行：

SELECT a.id, b.id, c.id) FROM (A a, B b) LEFT JOIN C c ON c.a_id = a.a_id AND c.b_id = b.b_id  

这样就可以执行了、