MySQL-左加入而不是
|
我试图避免子查询，因为它们通常比适当的连接具有更低的性能。
这是我当前无法正常工作的查询：
SELECT
a.`email_list_id`, a.`category_id`, a.`name`
FROM
`email_lists`AS a
LEFT JOIN `email_autoresponders` AS b
ON ( a.`website_id` = b.`website_id` )
WHERE
a.`website_id` = [...]
AND a.`category_id` <> 0
AND a.`email_list_id` <> b.`email_list_id`
GROUP BY
a.`email_list_id`
ORDER BY a.`name`
SELECT
`email_list_id`, `category_id`, `name`
FROM
`email_lists`
WHERE
`website_id` = [...]
AND `category_id` <> 0
AND `email_list_id` NOT IN (
SELECT
`email_list_id`
FROM
`email_autoresponders`
WHERE `website_id` = [...]
)
GROUP BY
`email_list_id`
ORDER BY
`name`
没有找到相关结果
已邀请:
2 个回复
需复
SELECT a.`email_list_id`, a.`category_id`, a.`name` FROM `email_lists`AS a LEFT JOIN `email_autoresponders` AS b ON ( a.`website_id` = b.`website_id` and a.`email_list_id` = b.`email_list_id` ) WHERE a.`website_id` = [...] AND a.`category_id` <> 0 AND b.`email_list_id` is NULL GROUP BY a.`email_list_id` ORDER BY a.`name`赣借
LEFT JOIN `email_autoresponders` AS b ON ( a.`website_id` = b.`website_id` AND a.`email_list_id` <> b.`email_list_id` )