仅选择mysql中的唯一行

这是怎么回事

SELECT T.id,T.name,T.userid 
FROM tbltest T 
GROUP BY T.userid
HAVING COUNT(T.userid) = 1;

试试这个:

SELECT T.id, T.name, T.userid, count(*) AS count FROM tbltest GROUP BY T.userid HAVING count = 1;

我不认为这是最快的方法。。。你可以试试:

SELECT T.id, T.name, T.userid, COUNT(*) AS num 
FROM tbltest T GROUP BY T.userid HAVING num = 1

或者

SELECT T.id, T.name, T.userid, COUNT(*) AS num FROM tbltest T
WHERE NOT EXISTS
(SELECT 1 FROM tbltest T2 WHERE T2.userid = T.userid AND T2.id != T.id)