Question

有一个包含5列的表格：id，data，category，time，page。我希望得到id＆gt;行given id和category = given category，按page对其进行分组，从time订购的每个网页获取第一个，并在其中减少page列行。（time不是唯一的）

我设法创建了这个查询并且它有效，但我想知道是否有更好的解决方案。我在选择合适的题名方面也遇到了问题，如果您认为它不完全是应该的话，请随时纠正我。

UPDATE `content` AS TABLE1
    INNER JOIN (SELECT MIN(TABLE2.`id`) AS ID, TABLE2.`page` FROM `content` AS TABLE2
        INNER JOIN (
            SELECT DISTINCT `page`, MIN(`time`) AS MINTIME
            FROM `content` 
            WHERE (`page` > (SELECT `page` FROM `content` WHERE `id` = ?) AND `category` = ?)
            GROUP BY `page`) AS TABLE3
        ON TABLE2.`page` = TABLE3.`page` AND TABLE2.`time` = TABLE3.MINTIME
        GROUP BY TABLE2.`page`) AS TABLE4
    ON TABLE1.`id` = TABLE4.ID
SET TABLE1.`page` = TABLE1.`page` - 1

Answer 1

这个怎么样？你不需要@变量，但我不想在SQL中使用问号：

SET @id:= <given id>;

UPDATE
  content c1 LEFT JOIN content c2 ON c1.page = c2.page AND 
                                     c1.category = c2.category AND 
                                     c2.time < c1.time AND c2.id > @id
SET c1.page=c1.page-1
WHERE 
  c1.id > @id AND
  c2.id IS NULL AND
  c1.category = '<given category>';

更新每个组的第一条记录

1 个答案: