Question

我正在尝试使用group by子句根据列 'last' 更新dt列。我需要通过hid，tid，tdate，fid，did，depid，acc 找到群组' 群组的最后日期“并设置 'dt'< / em> 此组中所有记录的值。

例如：

| id | hid | tid | tdate | fid | did | p2 | depid | acc | dt | last | |----------|-------|-----|------------|-----|-----|-------|-------|------|------|----------------------| | 3742030 | 12332 | 1 | 2017-09-02 | 1 | 1 | 9560 | 1 | 5334 | 1 | 2016-11-03T09:00:20Z | | 3799297 | 2386 | 1 | 2017-08-29 | 1 | 1 | 8480 | 1 | 5352 | 1 | 2016-11-03T11:12:55Z | | 4848877 | 2386 | 1 | 2017-08-29 | 1 | 1 | 8720 | 1 | 5352 | 2369 | 2016-12-17T16:59:22Z | | 10706343 | 12332 | 1 | 2017-09-02 | 1 | 1 | 9660 | 1 | 5334 | 2065 | 2017-03-01T12:32:27Z | | 14546682 | 2386 | 1 | 2017-08-29 | 1 | 1 | 11720 | 1 | 5352 | 4431 | 2017-05-12T10:24:09Z | | 15824920 | 12332 | 1 | 2017-09-02 | 1 | 1 | 10820 | 1 | 5334 | 1111 | 2017-07-15T05:19:04Z |

到

| id | hid | tid | tdate | fid | did | p2 | depid | acc | dt | last | |----------|-------|-----|------------|-----|-----|-------|-------|------|------|----------------------| | 3742030 | 12332 | 1 | 2017-09-02 | 1 | 1 | 9560 | 1 | 5334 | 1111 | 2016-11-03T09:00:20Z | | 3799297 | 2386 | 1 | 2017-08-29 | 1 | 1 | 8480 | 1 | 5352 | 4431 | 2016-11-03T11:12:55Z | | 4848877 | 2386 | 1 | 2017-08-29 | 1 | 1 | 8720 | 1 | 5352 | 4431 | 2016-12-17T16:59:22Z | | 10706343 | 12332 | 1 | 2017-09-02 | 1 | 1 | 9660 | 1 | 5334 | 1111 | 2017-03-01T12:32:27Z | | 14546682 | 2386 | 1 | 2017-08-29 | 1 | 1 | 11720 | 1 | 5352 | 4431 | 2017-05-12T10:24:09Z | | 15824920 | 12332 | 1 | 2017-09-02 | 1 | 1 | 10820 | 1 | 5334 | 1111 | 2017-07-15T05:19:04Z |

架构： http://sqlfiddle.com/#!9/4fad1d/1

是否有某种方法可以根据组更新表中的所有行？

由于

Answer 1

使用子查询加入表，该子查询将找到每个组的最新行。

update of t
join (
  select t1.*
  from of t1
  join (
    select hid,tid,tdate,fid,did,depid,acc, max(last) as last
    from of
    group by hid,tid,tdate,fid,did,depid,acc
  ) t2 using (hid,tid,tdate,fid,did,depid,acc,last)
) t3 using (hid,tid,tdate,fid,did,depid,acc)
set t.dt = t3.dt;

http://sqlfiddle.com/#!9/93708/2

对于子查询中的连接，您还可以使用NATURAL JOIN

  natural join (
    select hid,tid,tdate,fid,did,depid,acc, max(last) as last
    from of
    group by hid,tid,tdate,fid,did,depid,acc
  ) t2

http://sqlfiddle.com/#!9/e7e5ee/1

MySQL根据最大日期和组更新列中的所有值

1 个答案: