SQL CASE语句

Question

我的数据库表PE中有两个字段（BIT数据类型），而PER需要编写一个sql case语句来执行以下任务。

当PER = 0然后打印“非必需” 当PER = 1，则检查是否PE = 0然后打印“未完成”时PE = 1个打印“已完成”

以下是查询我试图而这是不工作

CASE pc.PER WHEN '0' THEN 'Not Required' 
            WHEN '1' THEN (CASE pc.PE WHEN '0' THEN 'Not Completed' 
         WHEN '1' THEN 'Completed') end as ab 

Answer 1

我想这可能是更容易把它写成：

CASE 
    WHEN pc.PER = '0' THEN 'Not Required' 
    WHEN pc.PER = '1' AND pc.PE = '0' THEN 'Not Completed' 
    ELSE 'Completed' 
END 

或者你就必须后添加在您的查询中：

CASE pc.PER WHEN '0' THEN 'Not Required' 
      WHEN '1' THEN (CASE pc.PE WHEN '0' THEN 'Not Completed' 
             WHEN '1' THEN 'Completed' 
          END) 
END AS ab 

Answer 2

您缺少一个结尾。

CASE pc.PER 
    WHEN 0 THEN 'Not Required' 
    WHEN 1 THEN 
     CASE pc.PE 
      WHEN 0 THEN 'Not Completed' 
      WHEN 1 THEN 'Completed' 
     END 
END as ab 

Answer 3

尝试下面的语句来代替：

CASE WHEN pc.PER =0 THEN 'Not Required' 
    WHEN pc.PER =1 THEN 
     CASE WHEN pc.PE = 0 THEN 'Not Completed' 
       WHEN pc.PE = 1 THEN 'Completed' 
    End 
End as ab