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語(yǔ)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(xún)結(jié)果進(jìn)行排序（無(wú)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(hù)的所有訂單并按每一個(gè)客戶(hù)下的訂單的金額 升序排序，同時(shí)給每一個(gè)客戶(hù)的訂單進(jìn)行編號(hào)。這樣就知道每個(gè)客戶(hù)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(hù)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(hù)所有的訂單中購(gòu)買(mǎi)的金額最小，而且并統(tǒng)計(jì)改訂單中，客戶(hù)是第幾次購(gòu)買(mǎi)的：

思路：利用臨時(shí)表來(lái)執(zhí)行這一操作。

1.先按客戶(hù)進(jìn)行分組，然后按客戶(hù)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(xún)查找出每一個(gè)客戶(hù)購(gòu)買(mǎi)時(shí)的最小價(jià)格。

3.根據(jù)查找出每一個(gè)客戶(hù)的最小價(jià)格來(lái)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(hù)第一次下的訂單。

思路。利用rows=1來(lái)查詢(xún)客戶(hù)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(kāi)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''