选择那些有多个条目的字段

Question

我不明白如何编写一个简单的sql语句，它只显示那些不止一次出现的条目 。

e.x.

NodeID Number 

0  12 
1  12 
2  12 
0  13 
1  13 
0  14 
1  15 
2  16 
1  17 

选择nodeID，number表，其中数出现一次以上不同nodeID

结果：

NodeID Number 
0  12 
1  12 
2  12 
0  13 
1  13 

Answer 1

SELECT a.* 
FROM TableName a 
     INNER JOIN 
     (
      SELECT Number 
      FROM TableName 
      GROUP BY Number 
      HAVING COUNT(*) > 1 
     ) b ON a.Number = b.Number 

• SQLFiddle Demo

另一种方法是使用EXISTS

SELECT a.* 
FROM TableName a 
WHERE EXISTS 
     (
      SELECT 1 
      FROM TableName b 
      WHERE a.Number = b.Number 
      GROUP BY Number 
      HAVING COUNT(*) > 1 
     ) 

• SQLFiddle Demo

Answer 2

试试这个

SELECT NodeID , Number FROM TableName WHERE Number IN 
(SELECT Number FROM TableName GROUP BY Number HAVING COUNT(*) > 1) 

Answer 3

你也可以使用EXISTS没有GROUP BY：

SELECT nodeid, 
     number 
FROM Table1 t1 
WHERE EXISTS(SELECT 1 
       FROM Table1 t2 
       WHERE t1.number = t2.number 
        AND t1.nodeid <> t2.nodeid) 

DEMO

Answer 4

我的第一个想法是做一个自我加入像下面，但它不会工作，因为分组发生之后。

SELECT T1.NodeId，T2.Number，COUNT（T2.Number）C FROM T1表 INNER JOIN表T2 USING（编号） WHERE C> 1 GROUP BY T2.Number

因此，你必须做分组首先选择，然后进行连接：

SELECT NodeId, Number 
FROM Table T1 
INNER JOIN (
    SELECT Number, COUNT(Number) C 
    FROM Table 
    WHERE C > 1 
    GROUP BY Number 
) T2 USING(Number)