ADO.NET学习笔记--CASE函数用法举例

1.单值判断，相当于switch case

CASE expression

WHEN value1 THEN returnvalue1

WHEN value2 THEN returnvalue2

WHEN value3 THEN returnvalue3

ELSE defaultreturnvalue

END

例子SELECT

SELECT FName,

(CASE FLevel WHEN 1 THEN 'VIP客户'

WHEN 2 THEN '高级客户'

WHEN 3 THEN '普通客户'

ELSE '客户类型错误'

END) as FLevelName

FROM T_Customer

2.相当于if…else…else….

CASE

WHEN condition1 THEN returnvalue1

WHEN condition 2 THEN returnvalue2

WHEN condition 3 THEN returnvalue3

ELSE defaultreturnvalue

END

例子：

SELECT FName, FWeight,

(CASE

WHEN FWeight<40 THEN ‘瘦瘦'

WHEN FWeight>50 THEN ‘肥肥'

ELSE 'ok'

END) as isnormal

FROM T_Person