请教一个统计分析语句

[Eric1006]

存在学员表
字段：
姓名 Name VARCHAR(20)
注册时间 RTime DATETIME
想计算每个月的已注册学员数量（非当月新注册学员数量），SQL语句怎么写？谢谢！

[htl258_Tony]

select convert(char(7),RTime,23) 月份,count(1) 学员数量
from 学员表
where datediff(mm,RTime,getdate())=0
group by convert(char(7),RTime,23)

[sgtzzc]

select month(RTime) as m,
cnt=(select count(1) from tb where datediff(mm,t.RTime,RTime)>=0)
from tb t
group by month(RTime)

[sgtzzc]

[Quote=引用 2 楼 sgtzzc 的回复:]
SQL code
select month(RTime) as m,
cnt=(select count(1) from tb where datediff(mm,t.RTime,RTime)>=0)
from tb t
group by month(RTime)
[/Quote]
嗯，加上年份比较好

select convert(varchar(7),RTime,120) as m,
cnt=(select count(1) from tb where datediff(mm,t.RTime,RTime)>=0)
from tb t
group by convert(varchar(7),RTime,120)

[东那个升]

select convert(char(7),RTime,114),(select count(*) from 学员表 where datediff(mm,RTime,a.RTime)>0) as num
from 学员表 a
group by  convert(char(7),RTime,114)

[东那个升]

每个月的已注册学员数量（非当月新注册学员数量），包含本月的吗