mysql - 选择具有多个条目的字段

Question

我不明白如何编写一个简单的 sql 语句，它只显示那些出现多次的条目。

前任

NodeID  Number

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

选择nodeID，number从表中出现多次不同的数字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 演示

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 演示

Answer 2

尝试这个

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

Answer 3

我的第一个想法是像下面这样进行自我加入，但它不起作用，因为分组发生在之后。

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

因此，您必须先进行分组选择，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)

Answer 4

您也可以EXISTS不使用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) 

演示