请帮助破解SQL查询以使用自联接或任何其他方式获取记录

Question

我有一个带有两列custid和flag的表Cust。并且有带有标志的记录u，i用于相同的custid。 我只想获取只有U而不是I的记录。 例如：

客户表：

custid  flag
123      U
123      I
124      U
124      I
125      U
126      U
126      I
127      U
127      U

我想选择custid 125和127，因为他们没有旗帜我。

请提出建议。

Answer 1

如果您将custid分组，则只能选择不存在flag = 'I'的那些。

select custid
from cust
group by custid
having count(case when flag = 'I' 
                  then 1 
                  else 0
             end) = 0

Answer 2

SELECT * FROM CUST
WHERE FLAG = 'U' AND
  CUSTID NOT IN (SELECT CUSTID FROM CUST WHERE FLAG = 'I')

Answer 3

这是另一种方法。 （的 Fiddle Example ）

select x.custId 
from cust x
      left join (select custId from cust where flag = 'I') y
      on x.custId = y.custId
where y.custId is null 
group by x.custId

Answer 4

select distinct custid from cust
MINUS
select distinct custid from cust where flag = 'I'

Answer 5

select distinct c.custid from cust c where (select count(*) 
from cust where custid = c.custid and flag = 'I') = 0

获取flag为'I'的客户的号码，如果是equal to 0，则选择custid。

Answer 6

select a.num, a.custid
from
(select count(flag) as num, custid
from cust
group by custid) as a
inner join 
(select count(flag) as num, custid
    from cust
    where flag = 'U'
    group by custid) as b
on a.custid = b.custid
and a.num = b.num

这是结果：