mysql - SQL INNER JOIN 与 DISTINCT 行？

Question

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

在这种情况下，如果我在“上传”中有 3 行具有匹配的 uniqueid/uploadgroup(如集合中的 3 次上传)，这会返回 3 行。

我正在寻找的是每个 DISTINCT COLLECTIONS.UNIQUEID 的一行 - 这可能吗？

所以当集合有

1 | title | idhere

和上传有

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

我正在回来

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

当我想要返回的只是

1 | title | uniqueID1

Answer 1

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