Oracle或者PostgreSQL的row_number over 排名语法

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。

这次我提供的表结构如下，

[sql] view
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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)

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)

第二种，带有完整的排名字段但是没有排序。

[sql] view
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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)

第三种， 没有任何排名字段，也没有任何排序字段。

[sql] view
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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)