row_number() over()分組排序功能:
在使用 row_number() over()函數時候,over()裏頭的分組以及排序的執行晚於 where 、group by、 order by 的執行。
例一:
表數據:
- 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:對查詢結果進行排序(無分組)
- select id,name,age,salary,row_number()over(order by salary desc) rn
- from TEST_ROW_NUMBER_OVER t
結果:
進一步排序:根據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
結果:
再一次排序:找出每一組中序號爲一的數據
- 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
結果:
排序找出年齡在13歲到16歲數據,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'
結果:結果中 rank 的序號,其實就表明了 over(order by salary desc) 是在where age between and 後執行的
例二:
1.使用row_number()函數進行編號,如
select email,customerID, ROW_NUMBER() over(order by psd) as rows from QT_Customer
原理:先按psd進行排序,排序完後,給每條數據進行編號。
2.在訂單中按價格的升序進行排序,並給每條記錄進行排序代碼如下:
select DID,customerID,totalPrice,ROW_NUMBER() over(order by totalPrice) as rows from OP_Order
3.統計出每一個各戶的所有訂單並按每一個客戶下的訂單的金額 升序排序,同時給每一個客戶的訂單進行編號。這樣就知道每個客戶下幾單了:
- select ROW_NUMBER() over(partition by customerID order by totalPrice)
- as rows,customerID,totalPrice, DID from OP_Order
4.統計每一個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',customerID from tabs
- group by customerID
5.統計每一個客戶所有的訂單中購買的金額最小,而且並統計改訂單中,客戶是第幾次購買的:
思路:利用臨時表來執行這一操作。
1.先按客戶進行分組,然後按客戶的下單的時間進行排序,並進行編號。
2.然後利用子查詢查找出每一個客戶購買時的最小价格。
3.根據查找出每一個客戶的最小价格來查找相應的記錄。
- 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等開窗函數時,over裏頭的分組及排序的執行晚於“where,group by,order by”的執行。
- select
- ROW_NUMBER() over(partition by customerID order by insDT) as rows,
- customerID,totalPrice, DID
- from OP_Order where insDT>'2011-07-22'