create table #tb
(id int,
 name varchar(10),
 pass int,
 mdate date)
insert into #tb
select 1, '张毛', 1, '2011-10-5'
union all
select 2, '黎明', 1, '2011-10-5'
union all
select 3, '张毛', 0, '2011-10-12'
union all
select 4, '张毛', 1, '2011-11-6'
go
select name,月份,合格率=convert(varchar(30),(SUM(pass)*1.0)/COUNT(*)*100 )+'%' from (
select name,月份=MONTH(mdate),pass from #tb) a group by name,月份

------解决方案--------------------
SQL code

declare @表ST table (id int,name varchar(4),PASS int,Mdate datetime)
insert into @表ST
select 1,'张毛',1,'2011-10-5' union all
select 2,'黎明',1,'2011-10-5' union all
select 3,'张毛',0,'2011-10-12' union all
select 4,'张毛',1,'2011-11-6'

select 姓名=name,月份=month(mdate),
合格率=ltrim(sum(pass)*100/count(1))+'%' from @表st 
group by name,month(mdate)
/*
姓名   月份          合格率
---- ----------- -------------
黎明   10          100%
张毛   10          50%
张毛   11          100%
*/

------解决方案--------------------
探讨

SELECT NAME,MONTH(MDATE) AS 月分,
SUM(CASE WHEN PASS=1 THEN 1.00 ELSE 0 END)/COUNT(1) 
FROM TB GROUP BY NAME,CONVERT(CHAR(6),MDATE,112)


------解决方案--------------------
SQL code

create table st
(
id int,
name  varchar(20),
pass int,
mdate date
)

insert into ST
select 1,'张毛',1,'2011-10-5' union all
select 2,'黎明',1,'2011-10-5' union all
select 3,'张毛',0,'2011-10-12' union all
select 4,'张毛',1,'2011-11-6'

select name, DATEPART(mm,mdate) months 
,cast(Round((cast(SUM(case when pass=1 then 1 else 0 end) AS float)/cast(COUNT(name) as float)),2)*100 as varchar)+'%' passPercent
from st
group by name,DATEPART(mm,mdate);