select *,ROW_NUMBER() over(partition by deviceID order by RecordDate desc
?
row_number() OVER (PARTITION BY COL1 ORDER BY COL2) 表示根據(jù)COL1分組，在分組內(nèi)部根據(jù) COL2排序，而此函數(shù)計(jì)算的值就表示每組內(nèi)部排序后的順序編號(hào)（組內(nèi)連續(xù)的唯一的)
實(shí)例：
初始化數(shù)據(jù)
create table employee (empid int ,deptid int ,salary decimal(10,2))
insert into employee values(1,10,5500.00)
insert into employee values(2,10,4500.00)
insert into employee values(3,20,1900.00)
insert into employee values(4,20,4800.00)
insert into employee values(5,40,6500.00)
insert into employee values(6,40,14500.00)
insert into employee values(7,40,44500.00)
insert into employee values(8,50,6500.00)
insert into employee values(9,50,7500.00)
數(shù)據(jù)顯示為
empid?????? deptid????? salary ----------- ----------- ---------------------------------------
1?????????? 10????????? 5500.00
2?????????? 10????????? 4500.00
3?????????? 20????????? 1900.00
4?????????? 20????????? 4800.00
5?????????? 40????????? 6500.00
6?????????? 40????????? 14500.00
7?????????? 40????????? 44500.00
8?????????? 50????????? 6500.00
9?????????? 50????????? 7500.00
需求：根據(jù)部門分組，顯示每個(gè)部門的工資等級(jí)
預(yù)期結(jié)果：
empid?????? deptid????? salary????????????????????????????????? rank ----------- ----------- --------------------------------------- --------------------
1?????????? 10????????? 5500.00???????????????????????????????? 1
2?????????? 10????????? 4500.00???????????????????????????????? 2
4?????????? 20????????? 4800.00???????????????????????????????? 1
3?????????? 20????????? 1900.00???????????????????????????????? 2
7?????????? 40????????? 44500.00???????????????????????????????1
6?????????? 40????????? 14500.00???????????????????????????????2
5?????????? 40????????? 6500.00???????????????????????????????? 3
9?????????? 50????????? 7500.00???????????????????????????????? 1
8?????????? 50????????? 6500.00???????????????????????????????? 2
SQL腳本：
SELECT *, Row_Number() OVER (partition by deptid ORDER BY salary desc) rank FROM employee
?
轉(zhuǎn)自： http://www.cnblogs.com/digjim/archive/2006/09/20/509344.html
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