mysql做法：
UPDATE table A
LEFT JOIN
table B
ON
A.B_ID = B.B_ID
SET
A.A_NAME = B.B_NAME;
SQLServer做法:
update A
set A_NAME = B.B_NAME
from table A left join table B
ON
A.B_ID = B.B_ID
MySQL与SQLServer的update left join语法区别
原文：http://www.cnblogs.com/king-/p/5301271.html