存储过程！！！
alter PROCEDURE get_count
@user_name varchar(30),
@table_name varchar(15),
@grade varchar(10),
@word varchar(10),
@number int output
AS
begin
set @user_name=@user_name+'_'+@table_name
declare @sql as varchar(1000)
if(@grade='不限')
begin
if(@word is null)
begin
set @sql='select @number=count(*) from '+@table_name+
' where id not in(select id from '+@user_name+')'
end
else
begin
set @sql='select @number=count(*) from '+@table_name+
' where 关键字= ''' + @word + '''
and id not in(select id from '+@user_name+')'
end
end
else 
begin
if(@word is null)
begin
set @sql ='select @number=count(*) from '+@table_name+'
where 级别=''' + @grade + '''
and id not in (select id from ' + @user_name + ')'
end
else
begin
set @sql = 'select @number=count(*) from '+@table_name+'
where 级别=''' + @grade + ''' and 关键字= ''' + @word + '''
and id not in (select id from ' + @user_name + ')'
end
end
print @sql
exec(@sql)
end
RETURN

declare @a int
exec get_count 'shanying','single_select','不限','管理学',@a output

数据库中是存在对应的表对应的项的，不过执行结果出错：消息 137，级别 15，状态 1，第 1 行
必须声明标量变量 "@number"。

print @sql的结果：select @number=count(*) from single_select where 关键字= '管理学'
and id not in(select id from shanying_single_select)


------解决方案--------------------
看最后一段.
--动态sql语句基本语法

SQL code

 
1 :普通SQL语句可以用Exec执行 

eg: Select * from tableName 
Exec('select * from tableName') 
Exec sp_executesql N'select * from tableName' -- 请注意字符串前一定要加N 

2:字段名，表名，数据库名之类作为变量时，必须用动态SQL 

eg: 
declare @fname varchar(20) 
set @fname = 'FiledName' 
Select @fname from tableName -- 错误,不会提示错误，但结果为固定值FiledName,并非所要。 
Exec('select ' + @fname + ' from tableName') -- 请注意 加号前后的 单引号的边上加空格 

当然将字符串改成变量的形式也可 
declare @fname varchar(20) 
set @fname = 'FiledName' --设置字段名 

declare @s varchar(1000) 
set @s = 'select ' + @fname + ' from tableName' 
Exec(@s) -- 成功 
exec sp_executesql @s -- 此句会报错 

declare @s Nvarchar(1000) -- 注意此处改为nvarchar(1000) 
set @s = 'select ' + @fname + ' from tableName' 
Exec(@s) -- 成功 
exec sp_executesql @s -- 此句正确 

3. 输出参数 
declare @num int, 
@sqls nvarchar(4000) 
set @sqls='select count(*) from tableName' 
exec(@sqls) 
--如何将exec执行结果放入变量中？ 

declare @num int, 
@sqls nvarchar(4000) 
set @sqls='select @a=count(*) from tableName ' 
exec sp_executesql @sqls,N'@a int output',@num output 
select @num