MySQL与SQLServer的update left join语法区别

需求： 

表A 字段 A_ID, A_NAME, B_ID 
表B 字段 B_ID, B_NAME 

需求把A的所有A_NAME更新为相应的B的 B_NAME。 

mysql做法： 

UPDATE A
LEFT JOIN
 B
ON
 A.B_ID = B.B_ID
SET
 A.A_NAME = B.B_NAME;

MSSQL做法： 

update A
set A_NAME = B.B_NAME
from A left join B
ON
 A.B_ID = B.B_ID
where  A.id=5