SQL IF..ELSE..在存储过程的使用规范

CREATE PROCEDURE [dbo].[sp_stat_info]
(
@city nvarchar(20),
@town nvarchar(20),
@village nvarchar(20)
)
as
declare @num numeric(10)
declare @yd_num numeric(10)
declare @lt_num numeric(10)
declare @gh_num numeric(10)
declare @xlt_num numeric(10)
select @num=count(jmzh) from jfxd.t_gongan_end_2
if @city='aaa'
begin
select @yd_num=count(jmzh) from jfxd.t_gongan_end_2 where SERIAL_NUMBER is not null
select @lt_num=count(jmzh) from jfxd.t_gongan_end_2 where unicom is not null
select @gh_num=count(jmzh) from jfxd.t_gongan_end_2 where tel is not null
select @xlt_num=count(jmzh) from jfxd.t_gongan_end_2 where little_tel is not null
end
else if @town='bbb'
begin
//sql语句
end
else
begin
//sql语句
end
update t_stat_info set……
GO