SQL - 如何找到一个只包含1的字段值

Question

我有一个表，可以像这样的记载：

member  value 
0001   1 
0001   2 
0001   3 
0002   1 
0002   2 
0003   1 

基本上就是我需要做的是检索成员3，因为他们只有一个记录的值为1.成员2的记录值为1和2，成员3的记录值为1,2和3.

请帮忙！

感谢

罗布

Answer 1

我会用NOT EXISTS与correlated subquery：

SELECT t.member, t.value 
FROM dbo.TableName t 
WHERE value = 1 
AND NOT EXISTS 
(
    SELECT 1 FROM dbo.TableName t2 
    WHERE t2.value <> 1 
    AND t.member = t2.member 
) 

Demo

如果您使用MS SQL-服务器NOT EXISTS也是最有效的方法在null上没有问题能够列。值得一读：http://www.sqlperformance.com/2012/12/t-sql-queries/left-anti-semi-join

Answer 2

此作品在Transact-SQL

SELECT member, value 
    FROM TableName 
    WHERE value IN 
    (SELECT value FROM TableName 
    GROUP BY value 
    HAVING COUNT(*) = 1) 

如果它发现他们所有的单个条目多个成员。

Answer 3

select member 
from (
select '0001' as member, 1 as value 
union 
select '0001' as member, 2 as value 
union 
select '0001' as member, 3 as value 
union 
select '0002' as member, 1 as value 
union 
select '0002' as member, 2 as value 
union 
select '0003' as member, 1 as value 
) members 
group by member 
having count(*) = 1 

Answer 4

有很多复杂的答案，作为发布的时间，但这个问题可以很简单地使用GROUP BY和HAVING回答：您正在使用

select member 
    from members_values 
group by member 
having count(value) = 1 

您还没有提到什么RDBMS但是AIUI，上面的代码应该是ANSI兼容的;它也假设你的桌子被称为members_values。

Answer 5

听起来你正在寻找发现，仅在该表中存在，一旦member ...

以下查询组由member和证明的次数是member出现在表格

SELECT member 
    , Count(*) As number_of_apperances 
FROM your_table 
GROUP 
    BY member 

现在我们用HAVING条款来限制这种聚合，只显示那些谁似乎只是一次记录：

SELECT member 
    , Count(*) As number_of_apperances 
FROM your_table 
GROUP 
    BY member 
HAVING Count(*) = 1 

Answer 6

试试这个：

SELECT member 
FROM MyTable 
GROUP BY member 
HAVING COUNT(value) = 1