MYSQL-實現ORACLE- row_number() over(partition by ) 分組排序功能

由於MYSQL沒有提供類似ORACLE中OVER()這樣豐富的分析函數.所以在MYSQL裏需要實現這樣的功能,我們只能用一些靈活的辦法:

1.首先我們來創建實例數據:

drop table if exists heyf_t10;
create table heyf_t10 (empid int ,deptid int ,salary decimal(10,2));

insert into heyf_t10 values
(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);

2. 確定需求: 根據部門來分組,顯示各員工在部門裏按薪水排名名次.

顯示結果預期如下:

+——-+——–+———-+——+
| 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 |
+——-+——–+———-+——+
3. SQL 實現

select empid,deptid,salary,rank from (
selectheyf_tmp.empid,heyf_tmp.deptid,heyf_tmp.salary,@rownum:=@rownum+1,
if(@pdept=heyf_tmp.deptid,@rank:=@rank+1,@rank:=1) as rank,
@pdept:=heyf_tmp.deptid
from (
select empid,deptid,salary from heyf_t10 order by deptid asc,salary desc
) heyf_tmp ,(select @rownum :=0 , @pdept := null ,@rank:=0) a )result
;

4. 結果演示

mysql> select empid,deptid,salary,rank from(
-> selectheyf_tmp.empid,heyf_tmp.deptid,heyf_tmp.salary,@rownum:=@rownum+1,
->if(@pdept=heyf_tmp.deptid,@rank:=@rank+1,@rank:=1) as rank,
-> @pdept:=heyf_tmp.deptid
-> from (
-> select empid,deptid,salary from heyf_t10 order bydeptid asc ,salary desc
-> ) heyf_tmp ,(select @rownum :=0 , @pdept := null,@rank:=0) a ) result
-> ;
+——-+——–+———-+——+
| 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 |
+——-+——–+———-+——+
9 rows in set (0.00 sec)

5.小結
此SQL正是利用了MYSQL的靈活以及用戶變量的調用. 希望大家可以通過此例舉一反三.寫出更多更精彩的SQL.

Comments

One Response to “MYSQL-實現ORACLE- row_number() over(partition by) 分組排序功能.”

ymhctt說道：

2011 年 04 月 25 日 下午 5:00

SELECT empid,deptid,salary,rank FROM
(SELECT a.empid,@dpo:=@dp,@dp:=a.deptid AS deptid,a.salary,IF(@dp@dpo,@id:=1,@id:=@id+1) AS rank
FROM (SELECT * FROM heyf_t10 ORDER BY deptid ASC,salary DESC )a,(SELECT @id:=0,@dp:=0,@dpo:=0) b) AS a
ORDER BY empid