3

我有一个 mysql 查询，它获取设计列表中的行。在这个列表中，我们有“普通”行，它们按它们的 id 排序，还有“特殊”行，它们按“special_end”（这是日期，现在在所有行中为 NULL）参数排序。因此，结果中的“特殊”行应该高于“正常”。

现在查询：

SELECT d.*, DATE_FORMAT(_created, '%d.%m.%Y') as _created_human, count(dp.id) photos_cnt, u.id user_id, u.class_name user_class_name, u.full_name user_full_name
FROM designs d
LEFT JOIN design_photo dp ON d.id=dp.design_id 
LEFT JOIN cms_user u ON d.cms_user_id=u.id
WHERE 1=1  AND d.status_id=1 AND d.published=1 AND u.cms_user_status_id=1 
GROUP BY d.id
ORDER BY d.special_end DESC, id DESC 
LIMIT 20 OFFSET 0

我需要在此查询中升级 ORDER BY 块以使用 special_end 参数和条件对行进行排序：

  • 如果 d.special_end >= DATE(NOW() ) -> 按 d.special_end DESC 排序，
  • 如果 d.special_end <= DATE(NOW() ) -> 按 id DESC 排序。

示例（id - row - special_end）：

515 design4 2012-07-21
514 design3 2012-06-30
526 design5 null
513 design2 2012-05-30 (this date is <= DATE( NOW() ))
512 design1 null
511 design0 null
.
.
.

我已经尝试写类似的东西

ORDER BY CASE d.special_end WHEN d.special_end >= DATE( NOW() ) THEN d.special_end WHEN d.special_end <= DATE( NOW() ) THEN d.id END DESC

或者

ORDER BY IF(d.special_end >= DATE( NOW() ), d.special_end, d.id) DESC

但没有结果。

谢谢你的帮助。

4

2 回答 2

3

按条件排序可能非常慢，我宁愿用它UNION来达到相同的结果：

SELECT t.* FROM (
    (
        SELECT d.*, DATE_FORMAT(_created, '%d.%m.%Y') as _created_human, count(dp.id) photos_cnt, u.id user_id, u.class_name user_class_name, u.full_name user_full_name
        FROM designs d
        LEFT JOIN design_photo dp ON d.id=dp.design_id 
        LEFT JOIN cms_user u ON d.cms_user_id=u.id
        WHERE d.special_end >= DATE(NOW()) AND d.status_id=1 AND d.published=1 AND u.cms_user_status_id=1 
        GROUP BY d.id
        ORDER BY d.special_end DESC
    ) UNION (
        SELECT d.*, DATE_FORMAT(_created, '%d.%m.%Y') as _created_human, count(dp.id) photos_cnt, u.id user_id, u.class_name user_class_name, u.full_name user_full_name
        FROM designs d
        LEFT JOIN design_photo dp ON d.id=dp.design_id 
        LEFT JOIN cms_user u ON d.cms_user_id=u.id
        WHERE (d.special_end < DATE(NOW()) OR d.special_end IS NULL) AND d.status_id=1 AND d.published=1 AND u.cms_user_status_id=1 
        GROUP BY d.id
        ORDER BY d.id DESC
    )
) t LIMIT 20 OFFSET 0
于 2012-06-22T08:22:54.973 回答
2

当有多个 Group by 或排序要求时，始终使用 UNION 拆分您的查询。只需使用 UNION 运算符拆分您的查询并进行排序。如下所示

Select * from Something where <condtion> order by 1 desc
UNION
Select * from Something where <condtion> order by 2 desc
于 2012-06-22T09:10:32.343 回答