Question

我将临时表t与这些查询一起使用，以便从comment表中删除重复的行：

CREATE TABLE t (
        id INT NOT NULL,
        hash BINARY(20),
    PRIMARY KEY(id),
    INDEX(hash) ) ENGINE=InnoDB;

INSERT INTO t (id, hash)
    SELECT id, UNHEX(SHA1(body))
        FROM `comment`;

DELETE FROM `comment`
       USING t AS t1,
             t AS t2
       WHERE t1.id = comment.id
         AND t2.hash = t1.hash AND t2.id < t1.id;

但是在删除阶段，出现此错误：

ERROR 1109 (42S02): Unknown table 'comment' in MULTI DELETE

我该如何解决？

Answer 1

MySQL在USING中不支持DELETE。我想你想要

DELETE c
    FROM `comment` c JOIN
         t t1
         ON t1.id = c.id JOIN
         t t2
         ON t2.hash = t1.hash AND t2.id < t1.id;

我怀疑有更简单的方法可以表达这种逻辑。也许您应该问另一个问题，包括样本数据，期望的结果以及对所实现逻辑的解释。

错误1109（42S02）：MULTI DELETE中的未知表

1 个答案: