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，
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。
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。
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。
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。
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。
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 ;
我们同样来执行第一种，第二种以及第三种查询，结果如下：
第一种，
CALL sp_rownumber('t1','i_name','rank','desc');query resulti_namerankrownumCharlie131Charlie122Charlie123Charlie114Charlie105Lily71Lily72Lily73Lily64Lily65Lily56Lily47Lucy21Lucy22Lucy13Ytt151Ytt152Ytt143Ytt144Ytt145
第二种，
CALL sp_rownumber('t1','i_name',NULL,NULL);query resulti_namerankrownumCharlie121Charlie132Charlie113Charlie124Charlie105Lily71Lily72Lily43Lily64Lily75Lily66Lily57Lucy21Lucy12Lucy23Ytt141Ytt142Ytt143Ytt154Ytt155
第三种，
CALL sp_rownumber('t1',NULL,NULL,NULL);query resulti_namerankrownumLily71Lucy22Ytt143Ytt144Charlie125Charlie136Lily77Lily48Ytt149Lily610Lucy111Lily712Ytt1513Lily614Charlie1115Charlie1216Lucy217Charlie1018Lily519Ytt1520