mysql - MySQL：选择查询，然后从该查询中删除列相等的记录

Question

这是我的初始查询：

SELECT bid_tag.*
FROM bid_tag join
     (select serial_number, count(*) as cnt
      from bid_tag where user_id = 0
      group by serial_number
     ) tsum
     on tsum.serial_number = bid_tag.serial_number and cnt > 1
order by bid_tag.serial_number
LIMIT 0, 21000;

现在从这些结果中，我需要选择所有位置tag_design = 0 AND tag_size = 0，然后DELETE从数据库中选择这些记录。

我只是不知道如何对初始查询的结果运行查询。

Answer 1

只需替换SELECT为DELETE，它将删除已选择的行。

DELETE bid_tag.*
FROM bid_tag join
     (select serial_number, count(*) as cnt
      from bid_tag where user_id = 0
      group by serial_number
     ) tsum
     on tsum.serial_number = bid_tag.serial_number and cnt > 1
WHERE tag_design = 0 AND tag_size = 0
order by bid_tag.serial_number
LIMIT 0, 21000;

Answer 2

EXISTS在 where 子句中使用一个术语：

DELETE
  FROM bid_tag btd
 WHERE EXISTS (
           SELECT 1
             FROM (
                     SELECT bid_tag.*
                       FROM bid_tag bts
                       JOIN (
                               SELECT serial_number, count(*) as cnt
                                 FROM bid_tag btj
                                WHERE btj.user_id = 0
                             GROUP BY btj.serial_number
                            ) tsum
                         ON (     tsum.serial_number = bts.serial_number
                              AND tsum.cnt > 1
                            )
                      WHERE bts.tag_design = 0
                        AND bts.tag_size = 0
                   ORDER BY bts.serial_number
                      LIMIT 0
                          , 21000
                  ) rs_base
            WHERE rs_base.id = btd.id   -- PK column
      )
      ;

术语中的子查询EXISTS可以进一步嵌套，以包含对原始结果集的另一个查询。只需确保始终选择要执行删除的表的主键。

请注意，您可能不想在删除操作中将自己限制在结果集中的一部分，因此请检查您是否需要限制前 21000 个结果 - 如果不需要，请删除“ORDER BY”和“LIMIT”子句.