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，
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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。
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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
)
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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。
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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
)
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第二种，带有完整的排名字段但是没有排序。
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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
)
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第三种， 没有任何排名字段，也没有任何排序字段。
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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
)
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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。
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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 result
| i_name | rank | rownum |
| 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 |
第二种，
query result
| i_name | rank | rownum |
| Charlie | 12 | 1 |
| Charlie | 13 | 2 |
| Charlie | 11 | 3 |
| Charlie | 12 | 4 |
| Charlie | 10 | 5 |
| Lily | 7 | 1 |
| Lily | 7 | 2 |
| Lily | 4 | 3 |
| Lily | 6 | 4 |
| Lily | 7 | 5 |
| Lily | 6 | 6 |
| Lily | 5 | 7 |
| Lucy | 2 | 1 |
| Lucy | 1 | 2 |
| Lucy | 2 | 3 |
| Ytt | 14 | 1 |
| Ytt | 14 | 2 |
| Ytt | 14 | 3 |
| Ytt | 15 | 4 |
| Ytt | 15 | 5 |
第三种，
query result
| i_name | rank | rownum |
| 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 |
本文转自 david_yeung 51CTO博客，原文链接：http://blog.51cto.com/yueliangdao0608/1350445，如需转载请自行联系原作者
