Mysql 具有不同行的SQL内部联接？

在本例中，如果在“uploads”中有3行具有匹配的uniqueid/uploadgroup（如集合中的3个uploads），则返回3行

我要找的是每个不同的集合对应一行。UNIQUEID-这可能吗

那么，当集合

SELECT collections.title, collections.uniqueID, uploads.uniqueID as thumb 
FROM collections 
INNER JOIN uploads ON collections.uniqueID = uploads.uploadGroup 
WHERE collections.owner = @owner

并且上传已经完成

1 | title | idhere

我现在回来了

1 | uniqueID1 | idhere
2 | uniqueID2 | idhere
3 | uniqueID3 | idhere

当我只想回来的时候

1 | title | uniqueID1
2 | title | uniqueID2
3 | title | uniqueID3

这里有一种方法（仅限sql server）：

---

如果您需要上传表中的一个简单的不同列表，那么您可以这样做：

SELECT collections.title, collections.uniqueID, uploads.uniqueID as thumb 
FROM collections
CROSS APPLY (
    SELECT TOP 1 *
    FROM uploads
    WHERE collections.uniqueID = uploads.uploadGroup
    ORDER BY uploads.uniqueID -- not required, can be changed to any column you want
) uploads

---

为什么

1 | title | uniqueID1

不是

1 | title | uniqueID3

？这类决定有何标准？PS：您需要选择

mysql

或

SQLServer

。解决方案将是特定于供应商的，您可以按标题分组，也可以选择前1行。你必须做出决定。

SELECT collections.title, collections.uniqueID, uploads.uniqueID as thumb 
FROM collections
CROSS APPLY (
    SELECT TOP 1 *
    FROM uploads
    WHERE collections.uniqueID = uploads.uploadGroup
    ORDER BY uploads.uniqueID -- not required, can be changed to any column you want
) uploads

SELECT collections.title, collections.uniqueID, uploads.uniqueID as thumb 
FROM collections 
INNER JOIN (SELECT DISTINCT uniqueID FROM uploads) uploads ON collections.uniqueID = uploads.uploadGroup 
WHERE collections.owner = @owner

SELECT collections.title, collections.uniqueID, min(uploads.uniqueID) as thumb 
FROM collections 
JOIN uploads ON collections.uniqueID = uploads.uploadGroup 
WHERE collections.owner = @owner
GROUP BY collections.title, collections.uniqueID