每个城市中属于每种类别的消费者的数量
select city,no_orders,upto_two_orders,more_than_two_orders from
(
select c.customerid,city,
case
when count(orderid) = 0 then 'no_orders'
when count(orderid) <=2 then 'upto_two_orders'
when count(orderid) >2 then 'more_than_two_orders'
end as category
from customers as c
left outer join orders as o on c.customerid = o.customerid
group by c.customerid,city
) as D
pivot
(
count(customerid) for category in ([no_orders],[upto_two_orders],[more_than_two_orders])
) as P
---统计五年中所有人的借书情况（类似于翻转）可进一步思考，比如我想查十年的。。。
select a.employeename,[2008],[2009],[2010],[2011],[2012] from (
select Borrower,count(borrowbookid) borrowbookcount,
case
when BorrowDate > '2012-1-1' then '2012'
when BorrowDate > '2011-1-1' then '2011'
when BorrowDate > '2010-1-1' then '2010'
when BorrowDate > '2009-1-1' then '2009'
when BorrowDate > '2008-1-1' then '2008'
else '2008年以前' end as borrowYear
from BorrowBookRecords
group by Borrower,BorrowDate
) as d
pivot
(
sum(borrowbookcount) for d.borrowYear in ([2008],[2009],[2010],[2011],[2012])
) as g
left join employees a on g.Borrower = a.employeeid
