select hyxf=sum(case when credit<0 then credit else 0 end) FROM [dbo].[ServiceHistory] where userID=1 group by userID
CASE后面的都是条件啊 直接要跟WHEN的 2楼正解
--case的两种用法,详情参看联机帮助 语法 简单 CASE 函数:CASE input_expression WHEN when_expression THEN result_expression [ ...n ] [ ELSE else_result_expression ENDCASE 搜索函数:CASE WHEN Boolean_expression THEN result_expression [ ...n ] [ ELSE else_result_expression END
FROM [dbo].[ServiceHistory]
where userID=1
group by userID
语法
简单 CASE 函数:CASE input_expression
WHEN when_expression THEN result_expression
[ ...n ]
[
ELSE else_result_expression
ENDCASE 搜索函数:CASE
WHEN Boolean_expression THEN result_expression
[ ...n ]
[
ELSE else_result_expression
END