Question

我具有以下表格结构，

ID  TypeID  No
1   10  50
2   20  100

我需要通过检查No列值来获取TypeID列值，我做了如下操作，

  select case when ( TypeID = 10) THEN  NO END AS NO1,
  CASE when (TypeID = 20 ) THEN  NO END AS NO2  from SAMPLE_TABLE

但是它返回NULL

预期输出为

NO1 NO2
1  0

Answer 1

您可以使用条件聚合：

with sample_table(ID,TypeID,No) as
(
 select 1,   10,  50   union all
 select 2,   20,  100
)
select max(case when TypeID = 10 THEN  NO END) AS NO1,
       max(case when TypeID = 20 THEN  NO END) AS NO2  
 from sample_table;

NO1  NO2
---  ---
 50  100

编辑（取决于您的评论）：：如果No列属于bit类型，请考虑：

select max(case when TypeID = 10 THEN  NO+0 END) AS NO1,
       max(case when TypeID = 20 THEN  NO+0 END) AS NO2  
 from sample_table;

NO1  NO2
---  ---
1    0

Demo

Answer 2

在这里灵活的一般方法是使用ROW_NUMBER：

WITH cte AS (
    SELECT *, ROW_NUMBER() OVER (ORDER BY TypeID) rn
    FROM yourTable
)

SELECT
    MAX(CASE WHEN rn = 1 THEN No END) AS NO1,
    MAX(CASE WHEN rn = 2 THEN No END) AS NO2
FROM cte;

如何检查case语句中的列值

2 个答案: