Sql Server 与 MySql 在使用 update inner join 时的区别

Sql Server

-- 不使用别名
UPDATE
    tb_User
SET
    tb_User.pass = ''
FROM
    tb_User usr
INNER JOIN
    tb_Address addr
ON
    usr.nAddressFK = addr.nAddressID
WHERE
    usr.id=123

-- 使用别名
UPDATE
    usr
SET
    usr.pass = ''
FROM
    tb_User usr
INNER JOIN
    tb_Address addr
ON
    usr.nAddressFK = addr.nAddressID
WHERE
    usr.id=123

MySql

UPDATE
    mem_world AS mw1
INNER JOIN
    mem_world AS mw2
ON
    mw1.parentid = mw2.wid
SET
    mw1.level = mw2.level
WHERE
    mw2.baseid = 107
AND
    mw2.parentid = 0
AND
    mw2.size > 1

一个是先 SET 再关联，另外一个是先关联再 SET。