表结构：
CREATE TABLE [dbo].[Exam](
[S_date] [datetime] NOT NULL,
[Order_Id] [varchar](50) NOT NULL,
[Product_Id] [varchar](50) NOT NULL,
[Amt] [numeric](18, 0) NOT NULL
) ON [PRIMARY]
题目一: 写一条Sql语句查询前出100到199的记录
题目二: 写一条Sql语句删除重复[除时间外的所有字段字段相同]的记录,保留重复记录中时间最大的记录
题目三: 一条Sql语句查出年份,1月,2月,3月....12月的订单总数列表
题目四: 一条sql语句查询出年份,本月销量,上月销量,环比%,去年同期销量,同比%列表
第一题比较简单，前面也讲过，就不赘述。
第二题：
delete from Exam where S_date not in (
select e2.maxdt from
(
select Order_Id,Product_Id,Amt,MAX(S_date) as maxdt from Exam
group by Order_Id,Product_Id,Amt
) as e2
)
第三题：分两次组
select y,sum(c1) as m1,sum(c2) as m2,sum(c3) as m3,sum(c4) as m4,sum(c5) as m5,sum(c6) as m6,
sum(c7) as m7,sum(c8) as m8,sum(c9) as m9,sum(c10) as m10,sum(c11) as m11,sum(c12) as m12
from
(
select
y,
case m when 1 then c else 0 end as c1,
case m when 2 then c else 0 end as c2,
case m when 3 then c else 0 end as c3,
case m when 4 then c else 0 end as c4,
case m when 5 then c else 0 end as c5,
case m when 6 then c else 0 end as c6,
case m when 7 then c else 0 end as c7,
case m when 8 then c else 0 end as c8,
case m when 9 then c else 0 end as c9,
case m when 10 then c else 0 end as c10,
case m when 11 then c else 0 end as c11,
case m when 12 then c else 0 end as c12
from
(
select y,m,count(s_date) as c from
(
select datepart(year,convert(DateTime,s_date)) as y,
datepart(month,convert(DateTime,s_date)) as m ,
s_date from exam
) as T1
group by T1.y,T1.m
)
as T2
) as T3
group by T3.y
第三题：SQL相当复杂，不过只要理清了思路就很容易上手了，这里主要用到了left join on，语句如下：
select y1 年,m1 月,c1 本月销售额,
c2 上月销售额,
case when c2 is null or c2=0 then '无穷大'
else cast(cast((isnull(c1, 0)-isnull(c2,0))*100/isnull(c2, 0) as decimal(10,2)) as varchar(50))+'%' end as 环比增长 ,
c3 去年本月销售额,
case when c3 is null or c3=0 then '无穷大'
else cast(cast((isnull(c1, 0)-isnull(c3,0))*100/isnull(c3, 0) as decimal(10,2)) as varchar(50))+'%' end as 同比增长
from
(
select y1,m1,c1,c2,c3
from
(
select y1,m1,c1,c2 from
(
select y1,m1,sum(Amt) as c1 from
(
select datepart(year,convert(DateTime,s_date)) as y1,
datepart(month,convert(DateTime,s_date)) as m1 ,
Amt
from orders
) as T1
group by T1.y1,T1.m1
) o2
left join
(
select y2,m2,sum(Amt) as c2 from
(
select datepart(year,convert(DateTime,s_date)) as y2,
datepart(month,convert(DateTime,s_date)) as m2 ,
Amt from orders
) as T1
group by T1.y2,T1.m2
) o3
on o2.y1 = o3.y2 and o2.m1 = o3.m2 - 1
) as o4
left join
(
select y3,m3,sum(Amt) as c3 from
(
select datepart(year,convert(DateTime,s_date)) as y3,
datepart(month,convert(DateTime,s_date)) as m3,
Amt from orders
) as T1
group by T1.y3,T1.m3
) as o5
on o4.y1 = o5.y3 - 1 and o4.m1 = o5.m3
) as o6
年 月 本月销售额 上月销售额 环比 去年同期 同比
2012 3 230 420 -45.24% NULL 无穷大
2010 4 270 NULL 无穷大 300 -10.00%
2011 4 300 353 -15.01% 420 -28.57%
2012 4 420 463 -9.29% NULL 无穷大
2011 5 353 NULL 无穷大 463 -23.76%
2012 5 463 NULL 无穷大 NULL 无穷大
2011 11 492 240 105.00% NULL 无穷大
2011 12 240 NULL 无穷大 NULL 无穷大