在mysql查询中选择唯一的行

我有疑问

SELECT DISTINCT employer.id, employer.name
FROM employers 
LEFT JOIN positions ON positions.id = employers.id 
LEFT JOIN statuses ON statuses.position = positions.some 
WHERE statuses.number = 2

问题是，我需要从雇主那里得到一些独特的记录，但我得到了重复的记录，因为状态。数字会重复，比如2226777等等，我只需要抓取一次。

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我不想使用DISTINCT，还有其他方法吗？

按状态使用组

   SELECT employer.id, employer.name
    FROM employers 
     LEFT JOIN positions ON positions.id = employers.id 
     LEFT JOIN statuses ON statuses.position = positions.some 
    WHERE statuses.number = 2 GROUP BY employer.id

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使用GROUP BY on employer id，对于返回的每一行，您将只获得一条雇主记录：

SELECT employer.id, employer.name
FROM employers 
LEFT JOIN positions ON positions.id = employers.id 
LEFT JOIN statuses ON statuses.position = positions.some 
WHERE statuses.number = 2
GROUP BY employer.id

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首先，每当您在WHERE子句中引用一个左连接的列时，如

statuses.number=2

，都会否定左连接列，并强制其表现为内部连接列

第二，试试这个版本：

SELECT e.id, e.name
    FROM employers e
    WHERE EXISTS(SELECT 1
                     FROM positions p
                         INNER JOIN statuses s
                             ON p.some = s.position
                     WHERE p.id = e.id
                         AND s.number = 2)