条件CASE语句语法

Question

我需要帮助为视图编写case语句.基表有2列,我将引用:'Stage'和'YesNo'.

如果Stage列为1,并且YesNo列为1,我需要CASE语句在视图中将其显示为"No" 如果Stage列为1,YesNo列为0,我需要CASE语句在视图中将其显示为"是".如果Stage列为1,YesNo列为NULL,我需要CASE语句在视图中将其显示为NULL.如果舞台不是1,我需要YesNo列在视图中显示为NULL.

到目前为止,这是我的逻辑,我认为是正确的,但是当我尝试运行它时,我得到关于'AS'这个词的语法错误.有什么建议？

CASE 
    WHEN a.Stage = 1 and a.YesorNo = 1 THEN 'No' 
    ELSE WHEN a.Stage = 1 and a.YesorNo = 0 THEN 'Yes' 
END AS NewViewColumn

Answer 1

删除ELSE WHEN,如果你离开ELSE,那么它将返回null任何不符合剩余逻辑的项目:

CASE 
    WHEN a.Stage = 1 and a.YesorNo = 1 THEN 'No' 
    WHEN a.Stage = 1 and a.YesorNo = 0 THEN 'Yes' 
END AS NewViewColumn

或使用:

CASE 
    WHEN a.Stage = 1 and a.YesorNo = 1 THEN 'No' 
    WHEN a.Stage = 1 and a.YesorNo = 0 THEN 'Yes' 
    ELSE 'other'
END AS NewViewColumn