MYSQL delete语句不支持别名？

有一个表的数据比较大，然后需要进行关联删除，删除的时候发现如下SQL报错：

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DELETE FROM test.test1 a WHERE EXISTS (SELECT 1 FROM test.test2 b WHERE a.recordID=b.smsInfoID AND b.receiveTime <="2011-10-09
00:00:00" ) limit 1000;

报错如下：

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Error Code: 1064

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'a WHERE EXISTS (SELECT 1 FROM test.test2 b WHERE a.recordID=b.smsInf' at line 1

开始以为是exists的问题，于是更改成in再测试，也报同样错：

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DELETE FROM test.test1 a WHERE a.recordid IN (SELECT b.smsInfoID FROM test.test2 b WHERE b.receiveTime <= "2011-10-09
00:00:00") LIMIT 1000;

将别名去掉就可以了，将上面两个报错的SQL更改成如下形式就可以了：

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DELETE FROM test.test1 WHERE recordid IN (SELECT smsInfoID FROM test.test2 WHERE receiveTime <= "2011-10-09
00:00:00") LIMIT 1000;

DELETE FROM test.test1 WHERE EXISTS (SELECT 1 FROM test.test2 WHERE test1.recordID=test2.smsInfoID AND test2.receiveTime <= "2011-10-09
00:00:00") LIMIT 1000;

下面支持别名的语法：

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DELETE test.a FROM test.test1 a WHERE a.recordid IN (SELECT b.smsInfoID FROM test.test2 b WHERE b.receiveTime <= "2011-10-09 00:00:00") LIMIT 1000;