mySQL cross-db/table更新让我大吃一惊

Question

数据库A包含表X

数据库B包含表Y and Z

A.X包含字段order_number和dude

B.Y包含字段order,dude_number B.Z包含字段other_dude_number和dude_type

我想A.X.dude更新到B.Y.dude_number基于:(B.Y.order = A.X.order_number) AND ((B.Z.other_dude_number = B.Y.dude_number) AND (B.Z.dude_type = 6))

我一直在抽出mySQL查询两个小时试图让它工作.我几乎可以肯定我需要一个UNION,但是我对UNION不太熟悉使用它.

Answer 1

UPDATE A.X
  JOIN B.Y ON Y.`order` = X.order_number
  JOIN B.Z ON Z.other_dude_number = Y.dude_number
SET      X.dude = Y.dude_number
WHERE    Z.dude_type = 6