sql server自定义函数

CREATE function [dbo].[f_testFunc](
@v_id nvarchar(4000)
,@v_type nvarchar(4000)
)
returns NVARCHAR(4000) as
begin
declare @str_res NVARCHAR(4000);
declare @str_id NVARCHAR(4000);
declare @str_code NVARCHAR(4000);
declare @str_name NVARCHAR(4000);
SELECT @str_id = a.id,@str_code = a.event_code,@str_name = a.event_name
FROM app_event a
WHERE a.id = @v_id;
IF(@v_type='id')
RETURN @str_id
IF(@v_type='code')
RETURN @str_code
IF(@v_type='name')
RETURN @str_name return @str_name;
endGO