Oracle或者PostgreSQL的row_number over 排名語法

PostgreSQL 和Oracle 都提供了 row_number() over() 這樣的語句來進行對應的字段排名， 很是方便。  MySQL卻沒有提供這樣的語法。 

這次我提供的表結構如下，

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

我模擬了20條數據來做演示。

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，我們來對這樣的排名函數進行三種不同的執行方式1：
第一種，完整的帶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)

第二種，帶有完整的排名字段但是沒有排序。

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)

第三種， 沒有任何排名字段，也沒有任何排序字段。

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)