Question

这里的要点是从users表中获取尚未分配给特定组织的子用户。但是，如果将子用户分配给当前用户，则仍然包括它。

它有效，但我觉得语法可能更简单：

SELECT u.userId, u.firstName, u.lastName, u.username, u2.services_user_id
FROM user u
LEFT JOIN user u2 ON u.userId = u2.services_user_id
WHERE u.enabled = 1
AND u.organization_id = 1
AND u.userId NOT IN (
    SELECT services_user_id FROM user 
    WHERE organization_id = 2 
    AND services_user_id <> 19
    AND services_user_id IS NOT NULL
)

Answer 1

我想您可以通过在on子句

中移动过滤条件来简化查询，如下所示

SELECT u.userId, u.firstName, u.lastName, u.username, u2.services_user_id
FROM user u
LEFT JOIN user u2 ON u.userId = u2.services_user_id 
                  AND (u2.organization_id <> 2 OR u2.services_user_id = 19)
WHERE u.enabled = 1
AND u.organization_id = 1

示例数据集有助于验证两个查询的结果

Answer 2

我重写了我的查询以使用NOT EXISTS和SELECT 1 FROM用户。对于我的目的，这两者都更快，更有效。

SELECT u.userId, u.firstName, u.lastName, u.username
FROM user u
LEFT JOIN user u2 ON u.userId = u2.services_user_id
WHERE u.enabled = 1
AND u.organization_id = 14
AND NOT EXISTS (
            SELECT 1 FROM user u3 
            WHERE 
                u3.organization_id = 1
                AND u3.services_user_id <> 19
                AND u3.services_user_id IS NOT NULL 
                AND u.userId = u3.services_user_id
)

结果相同，但更干净，只能拉出我需要的东西。

有没有办法可以简化这个MySQL查询？

2 个答案: