Question

我有一个带有computerid，userid和其他几列的MySQL表。现在我想要一个查询，它将返回多个用户共享computerid值的所有记录。查找以下示例数据：

computerid  userid
100         5     
105         10    
110         6     
100         7     
101         11    
100         5     
105         10    
101         11

对于上面的数据集，mysql查询应返回以下结果，因为在这种情况下，computerid由两个用户ID共享。

computerid  userid
100         5     
100         7

Answer 1

你可以这样做：

SELECT DISTINCT T2.computerid, T2.userid
FROM (
    SELECT computerid
    FROM table1
    GROUP BY computerid
    HAVING COUNT(DISTINCT userid) > 1
) T1
JOIN table1 T2
ON T1.computerid = T2.computerid

结果：

computerid  userid
100         5
100         7

在（computerid）上添加索引以提高性能。

Answer 2

    SELECT DISTINCT(computerid) , userid FROM table  
WHERE computerid IN 
(SELECT DISTINCT(computerid)  FROM table GROUP BY computerid HAVING COUNT(computerid)>1)

Answer 3

SELECT DISTINCT a.computerid, a.userId
FROM table a
JOIN (
    SELECT computerId
    FROM table
    GROUP BY computerId
    HAVING COUNT(DISTINCT userId) > 1
) b ON a.computerId = b.computerId

Answer 4

没有子查询的解决方案

SELECT 
  t1.*
FROM table t1
LEFT JOIN table t2
  ON t1.computerid = t2.computerid AND t1.userid != t2.userid
WHERE
  t2.userid IS NOT NULL
GROUP BY
  t1.computerid, t1.userid;

假设有少数计算机拥有多个用户，这应该相对较快。

MySQL查询返回非唯一列组合

4 个答案: