Question

我有一张如下表格。

ID   NAME
1    JOHN
2    JANE
3    JACK

在一个简单的select语句中，如何从表中查询JOHN和JANE？

条件是：

我。结果必须返回JOHN和JANE。

II。如果从表中删除了JOHN或JANE，它将只返回空结果。

Answer 1

您可以使用GROUP BY/HAVING确保有2个匹配项：

SELECT  Name
FROM    T
WHERE   Name IN ('JOHN', 'JANE')
AND     EXISTS
        (   SELECT  1
            FROM    T
            WHERE   Name IN ('JOHN', 'JANE')
            HAVING  COUNT(DISTINCT Name) = 2
        );

或者你可以使用自我加入：

SELECT  a.Name
FROM    T a
        INNER JOIN T b
            ON a.Name != b.Name
WHERE   a.Name IN ('JOHN', 'JANE')
AND     b.Name IN ('JOHN', 'JANE');

<强> Examples on SQL Fiddle (MySQL)

<强> Examples on SQL Fiddle (Oracle)

<强> Examples on SQL Fiddle (Postgresql)

Answer 2

试试这个：

SELECT 
  GROUP_CONCAT( `NAME` ) as names
FROM `TABLE`
WHERE 1
   AND NAME IN ('JOHN','JANE')
HAVING names= 'JOHN,JANE'

Answer 3

创建一个函数JohnAndJaneBothExist()

2

SELECT * FROM TABLENAME 
WHERE
  JohnAndJaneBothExist and
  Name In ('John', 'Jane')

SQL - 仅在条件匹配时选择

3 个答案: