仅删除连续的重复行

Question

我已经从API收集了数据以建立历史记录。最初，我每五分钟保存一次[[all值。后来，我将程序更改为仅保存已更改的数据。

现在，我要清理旧数据并删除同一count和account中以前的记录中id不变的所有值。

account id      count   time
42      12147   492     2015-09-20 11:31:14.0
42      12147   492     2015-09-20 11:36:19.0 // delete
13      12147   246     2015-09-20 11:31:14.0
2       12253   183     2015-09-20 11:36:19.0
2       19684   805     2015-09-20 12:00:41.0 // note in next comment
2       19684   810     2015-09-20 12:05:41.0
2       19684   805     2015-09-20 12:10:41.0 // we had this combination, but don't delete this record because the previous value was different
2       19684   805     2015-09-20 12:15:41.0 // delete
2       19684   805     2015-09-20 12:20:41.0 // delete
2       19684   806     2015-09-20 12:25:41.0

我试图通过group by，account和id上的count解决此问题。但是，采用这种方法，它将删除
非连续

重复项，即，如果某个记录在一段时间后再次具有相同的值，则它将属于同一组。[我还考虑过编写一个小脚本，如果account，id和count与先前的记录相同，我将遍历所有数据并删除当前行，但是我很好奇一条SQL语句可能实现吗？

Answer 1

您可以使用以下查询：

DELETE history 
FROM history 
INNER JOIN (SELECT MIN(time) AS minTime, account, id, count
            FROM history
            GROUP BY account, id, count) AS h
ON history.account = h.account AND history.id = h.id AND history.count = h.count
WHERE history.time > h.minTime

Demo here
编辑：
完成编辑后，我认为OP的示例数据中仍然存在一些错误（time字段应按升序排列。
使用表中存在的PK的其他假设，您可以使用以下查询：
SELECT pk
FROM history AS h1
WHERE account = (SELECT account 
                 FROM history AS h2
                 WHERE h1.account = h2.account AND
                       h1.id = h2.id AND                       
                       h2.time < h1.time
                 ORDER BY time DESC 
                 LIMIT 1)
      AND
      id = (SELECT id 
            FROM history AS h2
            WHERE h1.account = h2.account AND
                  h1.id = h2.id AND                  
                  h2.time < h1.time
            ORDER BY time DESC 
            LIMIT 1)
      AND
      count = (SELECT count
               FROM history AS h2
               WHERE h1.account = h2.account AND
                     h1.id = h2.id AND                     
                     h2.time < h1.time
               ORDER BY time DESC 
               LIMIT 1)

为了识别
要删除的记录（请参见this demo）。
现在您可以使用NOT IN运算符轻松删除不需要的行：
DELETE FROM history 
WHERE pk IN (
SELECT x.pk
FROM (             
  SELECT pk
  FROM history AS h1
  WHERE 
     account = (SELECT account 
                FROM history AS h2
                WHERE h1.account = h2.account AND
                      h1.id = h2.id AND                       
                      h2.time < h1.time
                      ORDER BY time DESC 
                      LIMIT 1)

     AND

     id = (SELECT id 
           FROM history AS h2
           WHERE h1.account = h2.account AND
                 h1.id = h2.id AND                  
                 h2.time < h1.time
           ORDER BY time DESC 
           LIMIT 1)

     AND

     count = (SELECT count
              FROM history AS h2
              WHERE h1.account = h2.account AND
                    h1.id = h2.id AND                     
                    h2.time < h1.time
              ORDER BY time DESC 
              LIMIT 1)) AS x)

Demo here
编辑2：
使用变量来定位要删除的pk值可能会导致查询速度大大提高：
SELECT pk
FROM (
  SELECT pk, account, id, count, time,
         @rn := IF (account = @acc AND id = @id AND count = @count,
                    @rn + 1, 1) AS rn,
         @acc := account,
         @id := id,
         @count := count
  FROM history
  CROSS JOIN (SELECT @rn = 0, @acc = 0, @id = 0, @count = 0) AS vars
  ORDER BY account, id, time, count ) AS t
WHERE t.rn > 1

Demo here

Answer 2

您可以使用此（未调试的）代码删除除第一个以外的所有内容：

delete from history h1 
where exists (select h2 
              from history 
              where
                h1.account = h2.account and
                h1.id = h2.id and
                h1.count = h2.count and
                h1.time < h2.time
             )