从这里下载文件employees.txt，customers.txt，orders.txt

参考文章：http://www.cnblogs.com/wwan/archive/2011/02/24/1964279.html

使用package导入数据：http://www.cnblogs.com/tylerdonet/archive/2011/04/17/2017471.html

简单的聚合

从orders表中选择各个年份共有共有多少客户订购了商品

• 第一种写法，我们可以写成这样
  1select YEAR(o.orderdate) orderyear,COUNT(distinct(custid)) numCusts
  2from Sales.Orders o
  3group by YEAR(o.orderdate)
  4go

  要注意的是如果把group by YEAR(o.orderdata)换成group by orderyear就会出错，这里涉及到sql语句的执行顺序问题，有时间再了解一下　　　　　　　　　　

• 第二种写法，
  1select orderyear,COUNT(distinct(custid))numCusts
  2from (select YEAR(orderdate) as orderyear,custid from sales.orders) as D
  3group by orderyear
  4go

  在from语句中先得到orderyear，然后再select语句中就不会出现没有这个字段的错误了

• 第三种写法，
  1select orderyear,COUNT(distinct(custid)) numCusts
  2from (select YEAR(orderdate),custid from sales.orders) as D(orderyear,custid)
  3group by orderyear
  4go

  在as D后面加上选择出的字段，是不是更加的清楚明了呢！

• 第四种写法，with出场了
  1with c as(
  2select YEAR(orderdate) orderyear, custid from sales.orders)
  3select orderyear,COUNT(distinct(custid)) numCusts from c group by orderyear
  4go

  with可以使语句更加的经凑，下面是权威解释。　　
  　　　　
  指定临时命名的结果集，这些结果集称为公用表表达式 (CTE)。该表达式源自简单查询，并且在单条 SELECT、INSERT、UPDATE、MERGE 或 DELETE 语句的执行范围内定义。该子句也可用在 CREATE VIEW 语句中，作为该语句的 SELECT 定义语句的一部分。公用表表达式可以包括对自身的引用。这种表达式称为递归公用表表达式。　　　　　　　　　　　　　　　

　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　----MSDN

• 第五种写法，也可以借鉴第三种写法，这样使语句更加清楚明了，便于维护
  1 with c(orderyear,custid) as(
  2  select YEAR(orderdate),custid from sales.orders)
  3  select orderyear,COUNT(distinct(custid)) numCusts from c group by c.orderyear
  4  go

  上面5中写法都得到相同的结果，如下图1：图1
  　　

添加计算

• 现在要求要求计算出订单表中每年比上一年增加的客户数目，这个稍微复杂
  1 with yearcount as(
  2 select YEAR(orderdate) orderyear,COUNT(distinct(custid)) numCusts from sales.orders group by YEAR(orderdate))
  3 select cur.orderyear curyear,cur.numCusts curNumCusts,prv.orderyear prvyear,prv.numCusts prvNumCusts,cur.numCusts-prv.numCusts growth
  4 from yearcount cur left join yearcount prv on cur.orderyear=prv.orderyear+1
  5 go

  这里两次使用到with结果集。查询得到的结果如下图2
  
  图2

复杂的计算

• 查找所有美国雇员掌握的所有至少有一个订单的客户的客户id，查询语句如下
  1 with TheseEmployees as(
  2 select empid from hr.employees where country='USA'),
  3 CharacteristicFunctions as(
  4 select custid,
  5 case when custid in (select custid from sales.orders as o where o.empid=e.empid) then 1 else 0 end as charfun
  6 from sales.customers as c cross join TheseEmployees as e)
  7 select custid,min(charfun) from CharacteristicFunctions group by custid having min(charfun)=1
  8 go

  这里嵌套with语句，第with语句查找美国雇员的id，第二个语句使用这个结果和拥有客户的客户id和拥有关系标识做笛卡尔积运算。最后从这个笛卡尔积中通过标识找到最终的custid。
  结果如下图3
  
  图3

引用至： http://www.cnblogs.com/tylerdonet/archive/2011/04/18/2020225.html

CREATE TABLE #tempTotalCBM
( Appointid int,
  TotalCBM NUMERIC
)

INSERT INTO #tempTotalCBM (Appointid,TotalCBM)
SELECT H.APPOINTID,
CAST(( CASE H.TruckerConfirm WHEN 'D' THEN SUM(D.DELIVERYCBM) ELSE SUM(D.CBM) END ) AS NUMERIC) AS TotalCBM
FROM
(
    SELECT APPOINTID , TruckerConfirm
    FROM CCC_TAHEADER
    WHERE
    DATEDIFF(D,RECEIVEDATE,'2010-10-01') <= 0
    AND DATEDIFF(D,RECEIVEDATE,GETDATE()) >= 0
) H
INNER JOIN CCC_TADETAIL D
ON D.APPOINTID = H.APPOINTID
GROUP BY H.APPOINTID,H.TruckerConfirm

SELECT M.APPOINTID,M.LOADTYPE,N.TotalCBM,
 L_TruckSize3T, L_TruckSize5T, L_TruckSize8T, L_TruckSize10T, L_TruckSize12T,
 Size20, Size40, Size40R, Size40HQ, Size45,ReceiveDate
FROM CCC_TAHEADER M
INNER JOIN
#tempTotalCBM N
ON M.APPOINTID = N.Appointid

-- SELECT * FROM #tempTotalCBM
DROP TABLE #tempTotalCBM

with c as (
SELECT H.APPOINTID,
CAST(( CASE H.TruckerConfirm WHEN 'D' THEN SUM(D.DELIVERYCBM) ELSE SUM(D.CBM) END ) AS NUMERIC) AS TotalCBM
FROM
(
    SELECT APPOINTID , TruckerConfirm
    FROM CCC_TAHEADER
    WHERE
    DATEDIFF(D,RECEIVEDATE,'2010-10-01') <= 0
    AND DATEDIFF(D,RECEIVEDATE,GETDATE()) >= 0
) H
INNER JOIN CCC_TADETAIL D
ON D.APPOINTID = H.APPOINTID
GROUP BY H.APPOINTID,H.TruckerConfirm
)

SELECT M.APPOINTID,M.LOADTYPE,c.TotalCBM,
 L_TruckSize3T, L_TruckSize5T, L_TruckSize8T, L_TruckSize10T, L_TruckSize12T,
 Size20, Size40, Size40R, Size40HQ, Size45,ReceiveDate
FROM CCC_TAHEADER M
INNER JOIN
c
ON M.APPOINTID = c.Appointid