没有用于字符转换的字符串输出

Question

我有一个 Char(1( 可为空的列(区(，我想在 NULL 时输出"未分配";

我试过了

SELECT CASE District
WHEN NULL
THEN 'Not Assigned'
ELSE District
END AS District
,[Name]
,AgencyType
FROM cli_Agency

和

SELECT CASE CONVERT(VARCHAR, District)
WHEN NULL
THEN 'Not Assigned'
ELSE CONVERT(VARCHAR, District)
END AS District
,[Name]
,AgencyType
FROM cli_Agency

但显示的是 Null 而不是"未分配"。

Answer 1

只是一个语法问题

...
CASE WHEN District IS NULL THEN 'Not Assigned' ELSE District END AS District,
...

你也可以把它写成

IsNull(District,'Not Assigned') as District,

甚至

coalesce(District,'Not Assigned') as District,