語法格式：row_number() over(partition by 分組列 order by 排序列 desc)
row_number() over()分組排序功能：
在使用 row_number() over()函數(shù)時(shí)候，over()里頭的分組以及排序的執(zhí)行晚于 where 、group by、 order by 的執(zhí)行。
例一：
表數(shù)據(jù)：
create table TEST_ROW_NUMBER_OVER(
id varchar(10) not null,
name varchar(10) null,
age varchar(10) null,
salary int null
);
select * from TEST_ROW_NUMBER_OVER t;
insert into TEST_ROW_NUMBER_OVER(id,name,age,salary) values(1,'a',10,8000);
insert into TEST_ROW_NUMBER_OVER(id,name,age,salary) values(1,'a2',11,6500);
insert into TEST_ROW_NUMBER_OVER(id,name,age,salary) values(2,'b',12,13000);
insert into TEST_ROW_NUMBER_OVER(id,name,age,salary) values(2,'b2',13,4500);
insert into TEST_ROW_NUMBER_OVER(id,name,age,salary) values(3,'c',14,3000);
insert into TEST_ROW_NUMBER_OVER(id,name,age,salary) values(3,'c2',15,20000);
insert into TEST_ROW_NUMBER_OVER(id,name,age,salary) values(4,'d',16,30000);
insert into TEST_ROW_NUMBER_OVER(id,name,age,salary) values(5,'d2',17,1800);
一次排序：對(duì)查詢結(jié)果進(jìn)行排序（無分組）
select id,name,age,salary,row_number()over(order by salary desc) rn
from TEST_ROW_NUMBER_OVER t
結(jié)果：
進(jìn)一步排序：根據(jù)id分組排序
select id,name,age,salary,row_number()over(partition by id order by salary desc) rank
from TEST_ROW_NUMBER_OVER t
結(jié)果：
再一次排序：找出每一組中序號(hào)為一的數(shù)據(jù)
select * from(select id,name,age,salary,row_number()over(partition by id order by salary desc) rank
from TEST_ROW_NUMBER_OVER t)
where rank 2
結(jié)果：
排序找出年齡在13歲到16歲數(shù)據(jù)，按salary排序
select id,name,age,salary,row_number()over(order by salary desc) rank
from TEST_ROW_NUMBER_OVER t where age between '13' and '16'
結(jié)果：結(jié)果中 rank 的序號(hào)，其實(shí)就表明了 over(order by salary desc) 是在where age between and 后執(zhí)行的
例二：
1.使用row_number（）函數(shù)進(jìn)行編號(hào)，如
select email,customerID, ROW_NUMBER() over(order by psd) as rows from QT_Customer
原理：先按psd進(jìn)行排序，排序完后，給每條數(shù)據(jù)進(jìn)行編號(hào)。
2.在訂單中按價(jià)格的升序進(jìn)行排序，并給每條記錄進(jìn)行排序代碼如下：
select DID,customerID,totalPrice,ROW_NUMBER() over(order by totalPrice) as rows from OP_Order
3.統(tǒng)計(jì)出每一個(gè)各戶的所有訂單并按每一個(gè)客戶下的訂單的金額 升序排序，同時(shí)給每一個(gè)客戶的訂單進(jìn)行編號(hào)。這樣就知道每個(gè)客戶下幾單了：
select ROW_NUMBER() over(partition by customerID order by totalPrice)
as rows,customerID,totalPrice, DID from OP_Order
4.統(tǒng)計(jì)每一個(gè)客戶最近下的訂單是第幾次下的訂單：
with tabs as
(
select ROW_NUMBER() over(partition by customerID order by totalPrice)
as rows,customerID,totalPrice, DID from OP_Order
)
select MAX(rows) as '下單次數(shù)',customerID from tabs
group by customerID
5.統(tǒng)計(jì)每一個(gè)客戶所有的訂單中購買的金額最小，而且并統(tǒng)計(jì)改訂單中，客戶是第幾次購買的：
思路：利用臨時(shí)表來執(zhí)行這一操作。
1.先按客戶進(jìn)行分組，然后按客戶的下單的時(shí)間進(jìn)行排序，并進(jìn)行編號(hào)。
2.然后利用子查詢查找出每一個(gè)客戶購買時(shí)的最小價(jià)格。
3.根據(jù)查找出每一個(gè)客戶的最小價(jià)格來查找相應(yīng)的記錄。
with tabs as
(
select ROW_NUMBER() over(partition by customerID order by insDT)
as rows,customerID,totalPrice, DID from OP_Order
)
select * from tabs
where totalPrice in
(
select MIN(totalPrice)from tabs group by customerID
)
6.篩選出客戶第一次下的訂單。
思路。利用rows=1來查詢客戶第一次下的訂單記錄。
with tabs as
(
select ROW_NUMBER() over(partition by customerID order by insDT) as rows,* from OP_Order
)
select * from tabs where rows = 1
select * from OP_Order
7.注意：在使用over等開窗函數(shù)時(shí)，over里頭的分組及排序的執(zhí)行晚于“where，group by，order by”的執(zhí)行。
select
ROW_NUMBER() over(partition by customerID order by insDT) as rows,
customerID,totalPrice, DID
from OP_Order where insDT>'2011-07-22'
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