如何在Oracle中查找表中的特定值？

Question

假设我的表是TEST_123，它包含以下记录：

id |  cid | result
------------------
1  |  C-1 |   TAM
2  |  C-1 |   TAM
3  |  C-2 |   RAM
4  |  C-2 |   TAM
5  |  C-3 |   SAM
6  |  C-3 |   SAM

现在我想要这样的cid，它只有一种类型的结果，所以答案应该是C-1和C-3，而不是C-2，因为它有两种不同的结果。是否需要Oracle query来执行此操作？

Answer 1

您只需理解GROUP BY和HAVING子句。

答案很简单，就像

select cid
from TEST_123
group by cid
having count(distinct result) = 1

注意：group by从CID中选择不同的键；的 filters on条件对组中的所有记录都有效，在本例中为count(distinct result) = 1

Answer 2

使用是存在的，这有点棘手，因为每个组的结果应该是相同的

 select t1.* from TEST_123 t1 where exists(
             select 1 from TEST_123 t2 where t2.cid=t1.cid
                                      and t2.result=t1.result
                                      group by t2.cid,t2.result
                                      having count(*)=
                                       (select count(*) from TEST_123 t3
                                       where t3.cid=t2.cid)
                                      )

示例

with TEST_123 as
(
select 1 as id , 'c-1' as cid , 'tam' as result from dual
union all
select 2 as id , 'c-1' as cid , 'tam' as result from dual
union all
select 3 as id , 'c-2' as cid , 'tam' as result from dual
union all
select 4 as id , 'c-2' as cid , 'ram' as result from dual

)

select distinct t1.cid from TEST_123 t1 where exists(
                 select 1 from TEST_123 t2 where t2.cid=t1.cid
                                          and t2.result=t1.result
                                          group by t2.cid,t2.result
                                          having count(*)=
                                           (select count(*) from TEST_123 t3
                                           where t3.cid=t2.cid)
                                          )

demo

Answer 3

基于@zaynul的回答，这里是另一个变体：

with TEST_123 as
(
select 1 as id , 'c-1' as cid , 'tam' as result from dual
union all
select 2 as id , 'c-1' as cid , 'tam' as result from dual
union all
select 3 as id , 'c-2' as cid , 'tam' as result from dual
union all
select 4 as id , 'c-2' as cid , 'ram' as result from dual
)
select * from test_123 where cid in (
    select cid from test_123 group by cid having count(distinct result) = 1);