MySQL 实现Oracle的row_number over 这样的排名函数-同乐学堂

PostgreSQL 和Oracle 都提供了 row_number() over() 这样的语句来进行对应的字段排名，很是方便。 MySQL却没有提供这样的语法。
最近由于从Oracle 迁移到MySQL的需求越来越多，所以这样的转化在所难免。下面我在MySQL里面来实现这样的做法。

这次我提供的表结构如下，

[sql] view plain copy

Table "ytt.t1"
Column | Type | Modifiers
--------+-----------------------+-----------
i_name | character varying(10) | not null
rank | integer | not null

我模拟了20条数据来做演示。

[sql] view plain copy

t_girl=# select * from t1 order by i_name;
i_name | rank
---------+------
Charlie | 12
Charlie | 12
Charlie | 13
Charlie | 10
Charlie | 11
Lily | 6
Lily | 7
Lily | 7
Lily | 6
Lily | 5
Lily | 7
Lily | 4
Lucy | 1
Lucy | 2
Lucy | 2
Ytt | 14
Ytt | 15
Ytt | 14
Ytt | 14
Ytt | 15
(20 rows)

在PostgreSQL下，我们来对这样的排名函数进行三种不同的执行方式1：
第一种，完整的带有排名字段以及排序。

[sql] view plain copy

t_girl=# select i_name,rank, row_number() over(partition by i_name order by rank desc) as rank_number from t1;
i_name | rank | rank_number
---------+------+-------------
Charlie | 13 | 1
Charlie | 12 | 2
Charlie | 12 | 3
Charlie | 11 | 4
Charlie | 10 | 5
Lily | 7 | 1
Lily | 7 | 2
Lily | 7 | 3
Lily | 6 | 4
Lily | 6 | 5
Lily | 5 | 6
Lily | 4 | 7
Lucy | 2 | 1
Lucy | 2 | 2
Lucy | 1 | 3
Ytt | 15 | 1
Ytt | 15 | 2
Ytt | 14 | 3
Ytt | 14 | 4
Ytt | 14 | 5
(20 rows)

第二种，带有完整的排名字段但是没有排序。

[sql] view plain copy

t_girl=# select i_name,rank, row_number() over(partition by i_name ) as rank_number from t1;
i_name | rank | rank_number
---------+------+-------------
Charlie | 12 | 1
Charlie | 12 | 2
Charlie | 13 | 3
Charlie | 10 | 4
Charlie | 11 | 5
Lily | 6 | 1
Lily | 7 | 2
Lily | 7 | 3
Lily | 6 | 4
Lily | 5 | 5
Lily | 7 | 6
Lily | 4 | 7
Lucy | 1 | 1
Lucy | 2 | 2
Lucy | 2 | 3
Ytt | 14 | 1
Ytt | 15 | 2
Ytt | 14 | 3
Ytt | 14 | 4
Ytt | 15 | 5
(20 rows)

第三种，没有任何排名字段，也没有任何排序字段。

[sql] view plain copy

t_girl=# select i_name,rank, row_number() over() as rank_number from t1;
i_name | rank | rank_number
---------+------+-------------
Lily | 7 | 1
Lucy | 2 | 2
Ytt | 14 | 3
Ytt | 14 | 4
Charlie | 12 | 5
Charlie | 13 | 6
Lily | 7 | 7
Lily | 4 | 8
Ytt | 14 | 9
Lily | 6 | 10
Lucy | 1 | 11
Lily | 7 | 12
Ytt | 15 | 13
Lily | 6 | 14
Charlie | 11 | 15
Charlie | 12 | 16
Lucy | 2 | 17
Charlie | 10 | 18
Lily | 5 | 19
Ytt | 15 | 20
(20 rows)

MySQL 没有提供这样的语句，所以我用了以下的存储过程来实现。

[sql] view plain copy

DELIMITER $$
USE `t_girl`$$
DROP PROCEDURE IF EXISTS `sp_rownumber`$$
CREATE PROCEDURE `sp_rownumber`(
IN f_table_name VARCHAR(64),
IN f_column_partitionby VARCHAR(64),
IN f_column_orderby VARCHAR(64),
IN f_is_asc CHAR(4)
)
BEGIN
-- Created by ytt at 2014/1/10
-- Do a row_number() over()
DECLARE i INT;
-- Create a temporary table to save result.
DROP TABLE IF EXISTS tmp_rownum;
SET @stmt = CONCAT('create temporary table tmp_rownum select *,''rownum'' from ',f_table_name,' where 1 = 0');
PREPARE s1 FROM @stmt;
EXECUTE s1;
SET i = 0;
SET @j = 0;
SET @v_column_paritionby = '';
-- Check whether parition column is null or not.
IF (f_column_partitionby = '' OR f_column_partitionby IS NULL) THEN
-- No additional parition column.
SET @stmt = CONCAT('insert into tmp_rownum select *,@j:= @j+1 as rownum from ',
f_table_name);
PREPARE s1 FROM @stmt;
EXECUTE s1;
ELSE
-- Give partition column.
SET @stmt = CONCAT('select count(*) from (select count(*) from ',f_table_name,' group by ',
f_column_partitionby,') as a into @cnt');
PREPARE s1 FROM @stmt;
EXECUTE s1;
WHILE i < @cnt
DO
-- Get the partition value one by one.
SET @stmt = CONCAT('select ',f_column_partitionby,' from ',f_table_name,' group by ',f_column_partitionby,' limit ',i,',1 into @v_column_partitionby');
PREPARE s1 FROM @stmt;
EXECUTE s1;
-- Check whether sort is needed.
IF f_column_orderby = '' OR f_column_orderby IS NULL THEN
SET @stmt = CONCAT('insert into tmp_rownum select *,@j:= @j+1 as rownum from ',
f_table_name,' where ',f_column_partitionby,' = ''',@v_column_partitionby,'''');
ELSE
SET @stmt = CONCAT('insert into tmp_rownum select *,@j:= @j+1 as rownum from ',
f_table_name,' where ',f_column_partitionby,' = ''',@v_column_partitionby,'''
order by ',f_column_orderby,' ',f_is_asc);
END IF;
SET @j = 0;
PREPARE s1 FROM @stmt;
EXECUTE s1;
SET i = i + 1;
END WHILE;
END IF;
-- Reset all session variables.
SET @j = NULL;
SET @v_column_paritionby = NULL;
SET @cnt = NULL;
SELECT * FROM tmp_rownum;
END$$
DELIMITER ;