[英]How to return an ID for the row that has MIN/MAX value within a group?
SELECT
MAX(`client_id`) `client_id`
FROM
`phrases`
WHERE
`language_id` = 1 AND
`client_id` = 1 OR
`client_id` IS NULL
GROUP BY
`language_phrase_id`
如何获取包含MAX(`client_id`)
值的行的id
?
我需要在派生表的上下文中,例如
SELECT
`p2`.`phrase`
FROM
(SELECT `language_phrase_id`, MAX(`client_id`) `client_id` FROM `phrases` WHERE `language_id` = 1 AND `client_id` = 1 OR `client_id` IS NULL GROUP BY `language_phrase_id`) `p1`
INNER JOIN
`phrases` `p2`
ON
`p2`.`language_id` = 1 AND
`p1`.`language_phrase_id` = `p2`.`language_phrase_id` AND
`p1`.`client_id` = `p2`.`client_id`;
我在理解需求时遇到了一些麻烦,但这似乎正是您要寻找的。
不是最漂亮的SQL,我敢肯定它可以简化,而是一个起点。
SELECT p1.id, p1.phrase
FROM phrases p1
LEFT JOIN `phrases` p2
ON p1.language_id=p2.language_id
AND p1.language_phrase_id=p2.language_phrase_id
AND p1.client_id IS NULL and p2.client_id = 1
WHERE p2.id IS NULL AND p1.language_id=1
AND (p1.client_id=1 or p1.client_id IS NULL)
GROUP BY p1.language_phrase_id
使用窗口函数查找每个组的最大值,然后使用where
子句选择具有最大值的行:
select p.*
from (SELECT p.*, max(client_id) partition by (language_phrase_id) as maxci
from phrases p
WHERE (`language_id` = 1 AND `client_id`= 1) or
`client_id` IS NULL
) p
where client_id = maxci
我还添加了括号以阐明您的where
语句。 混合and
和or
,我总是使用括号以避免可能出现的混乱和错误。
现在,您已将mysql
标记添加到语句中,这将不起作用。 因此,这是一个特定于MySQL的解决方案:
select language_phrase_id,
substring_index(group_concat(id order by client_id desc), ',', 1) as max_id
from phrases
group by phrases p
请注意,此if id
将在此过程中转换为字符串。 如果类型不同,则可以将其转换回来。
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