使用其他列中的最大值更新每个组的行

发布于 2024-09-09 08:43:53 字数 522 浏览 4 评论 0原文

我必须更新一个非常非常大的表中的一列。所以性能是一个大问题。

问题与此类似一个，但仅适用于 Sybase Adaptive Server Enterprise (ASE 12.5.4)，而且我需要对检索到的行进行更新。有没有一种方法可以在不使用自连接的情况下实现这一点，就像 Oracle 投票最高的答案中那样？

这是第一次尝试连接，但它是按照命令减慢其预期的表的速度：

UPDATE table SET flag = 1
FROM table AS a1
LEFT OUTER JOIN table AS a2
ON (a1.groupId = a2.groupId AND a1.id < a2.id)
WHERE a2.groupId IS NULL
and a1.somename in ('x', 'y')

原文

I have to update a column in a very, very large table. So performance is a big issue.

The question is the similar to this one, but only for Sybase Adaptive Server Enterprise (ASE 12.5.4) plus I need to do an update on the retrieved rows. Is there a way to do it without a self join like in the top voted answer for Oracle?

This was the first attempt with a join, but it is by orders to slow for the table it is intended for:

UPDATE table SET flag = 1
FROM table AS a1
LEFT OUTER JOIN table AS a2
ON (a1.groupId = a2.groupId AND a1.id < a2.id)
WHERE a2.groupId IS NULL
and a1.somename in ('x', 'y')

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对你的占有欲 2024-09-16 08:43:53

会……

UPDATE table AS t1 SET flag = 1
    WHERE t1.somename IN ('x', 'y') AND
          t1.id = (SELECT MAX (t2.id)
                    FROM table t2
                    WHERE t2.groupId = t1.groupId);

有什么帮助吗？

Would...

UPDATE table AS t1 SET flag = 1
    WHERE t1.somename IN ('x', 'y') AND
          t1.id = (SELECT MAX (t2.id)
                    FROM table t2
                    WHERE t2.groupId = t1.groupId);

be any help?

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