Question

问题解决了！

更新

不太正确我需要的东西，让我们在带有字段ID，NAME，COVER

的简单表上做例子

我有100个条目有100个名字，有些名称是重复的，但我只想从重复项中更新第一个。

尝试更新数据库中所有重复项的所有第1行，真的很难做到，我知道如何制作它？下面是我试图重建的代码，但是这个代码用最后一个替换所有重复的代码。

架构，我希望它如何工作

ID NAME COVER
1  Max   1
2  Max   0
3  Andy  1
4  Andy  0
5  Andy  0

UPDATE table t
  JOIN (
    SELECT MinID, b.Name LatestName
    FROM table b
    JOIN (
      SELECT MIN(ID) MinID, MAX(ID) MaxID
      FROM table
      GROUP BY tag
      HAVING COUNT(*) > 1
    ) g ON b.ID = g.MaxID
  ) rs ON t.ID = rs.MinID
SET t.Name = LatestName;

Answer 1

根本不清楚你想要什么。也许这个：

UPDATE table AS t
  JOIN 
    ( SELECT MIN(ID) MinID
      FROM table
      GROUP BY Name
      HAVING COUNT(*) > 1
    ) AS m 
    ON t.ID = m.MinID
SET t.Cover = 1 ;

对于这个（和将来的）问题，请记住，当你写一个问题时：

1. a description of your problem, as clear as possible    --- you have that
2. data you have now (a few rows of the tables)           --- ok, nice
3. the code you have tried                 --- yeah, but better use same names
                                           --- as the data and description above
4. the error you get (if you get an error)      --- doesn't apply here
5. the result you want (the rows after the update in your case)
                                       --- so we know what you mean in case we 
                                       --- haven't understood from all the rest

Answer 2

我最近在PostgreSQL中做过这个。您是否可以使用临时表？如果是这样，对于每个重复集，将MIN（）主键插入临时表，然后使用临时表中的PK使用where子句执行UPDATE。

编辑：关注你的评论，这是我最近做的事情。

CREATE TEMPORARY TABLE misc_updates (
    temp_oid INTEGER,
    job INTEGER,
    run CHARACTER VARYING(8),
    quantity INTEGER
);

INSERT INTO misc_updates (temp_oid, job, run, quantity)
SELECT
    MAX(runjob.oid) temp_oid, runjob.job, runjob.run, SUM(runjob.quantity) sum_quantity
FROM
    runjob
INNER JOIN job ON (runjob.job = job.code)
INNER JOIN
    (SELECT run, job FROM runjob GROUP BY run, job HAVING COUNT(*) > 1) my_inner
    ON (runjob.run = my_inner.run AND runjob.job = my_inner.job)
GROUP BY
    runjob.job, runjob.run, job.quantity
;

/* Do updates on one of the duplicated runjob rows */
UPDATE runjob
    SET quantity = mu.quantity
FROM
    misc_updates mu
WHERE
    runjob.oid = mu.temp_oid;

您可以将'oid'替换为主键（我的问题是该表没有主键！）。同样重要的是UPDATE中的where子句，因此只更新了一些行。您需要将MAX（）替换为MIN（），当然还要将行更改为用例中的行。请记住，这适用于PostgreSQL，但方法应该大致相同。

Answer 3

使用子查询作为选择标准：

UPDATE table t SET t.Name = LatestName
WHERE ID = 
    (SELECT ID FROM table WHERE 
         (
            SELECT COUNT(DISTINCT(Name)) FROM table WHERE Name = 'duplicate'
         ) > 1 
     LIMIT 1)

仅更新MySQL中重复条目的第一条记录

3 个答案: