PostgreSQL窗口函数测试

简单记录下

测试数据如下：

表结构

 \d products数据表 "public.products"栏位     |          类型          | 校对规则 |  可空的  |                     预设
--------------+------------------------+----------+----------+----------------------------------------------product_id   | integer                |          | not null | nextval('products_product_id_seq'::regclass)product_name | character varying(255) |          | not null |price        | numeric(11,2)          |          |          |group_id     | integer                |          | not null |
索引："products_pkey" PRIMARY KEY, btree (product_id)
外部键(FK)限制："products_group_id_fkey" FOREIGN KEY (group_id) REFERENCES product_groups(group_id)postgres=# \d product_groups数据表 "public.product_groups"栏位    |          类型          | 校对规则 |  可空的  |                       预设
------------+------------------------+----------+----------+--------------------------------------------------group_id   | integer                |          | not null | nextval('product_groups_group_id_seq'::regclass)group_name | character varying(255) |          | not null |
索引："product_groups_pkey" PRIMARY KEY, btree (group_id)
由引用：TABLE "products" CONSTRAINT "products_group_id_fkey" FOREIGN KEY (group_id) REFERENCES product_groups(group_id)

数据：

postgres=# table products;product_id |    product_name    |  price  | group_id
------------+--------------------+---------+----------1 | Microsoft Lumia    |  200.00 |        12 | HTC One            |  400.00 |        13 | Nexus              |  500.00 |        14 | iPhone             |  900.00 |        15 | HP Elite           | 1200.00 |        26 | Lenovo Thinkpad    |  700.00 |        27 | Sony VAIO          |  700.00 |        28 | Dell Vostro        |  800.00 |        29 | iPad               |  700.00 |        310 | Kindle Fire        |  150.00 |        311 | Samsung Galaxy Tab |  200.00 |        3
(11 行记录)postgres=# table product_groups;group_id | group_name
----------+------------1 | Smartphone2 | Laptop3 | Tablet
(3 行记录)

avg1是整个部门算平均值，avg2是同一部内当前行与之前的行的记录算平均值，因为w1没有指定range，因此默认使用between unbounded preceding and current rowselect t1.group_name,t2.product_id,t2.product_name,t2.price,
avg(t2.price) over w2 as avg1 ,
avg(t2.price)  over w1 as avg2 ,
first_value(t2.price) over w1,
last_value(t2.price) over w2 
from product_groups t1,products t2 where t1.group_id=t2.group_id
window w1 as (partition by t1.group_name order by t2.price) , 
window w2 as (partition by t1.group_name order by t2.price range between unbounded preceding and unbounded following);group_name | product_id |    product_name    |  price  |         avg1         |         avg2         | first_value | last_value
------------+------------+--------------------+---------+----------------------+----------------------+-------------+------------Laptop     |          7 | Sony VAIO          |  700.00 | 850.0000000000000000 | 700.0000000000000000 |      700.00 |    1200.00Laptop     |          6 | Lenovo Thinkpad    |  700.00 | 850.0000000000000000 | 700.0000000000000000 |      700.00 |    1200.00Laptop     |          8 | Dell Vostro        |  800.00 | 850.0000000000000000 | 733.3333333333333333 |      700.00 |    1200.00Laptop     |          5 | HP Elite           | 1200.00 | 850.0000000000000000 | 850.0000000000000000 |      700.00 |    1200.00Smartphone |          1 | Microsoft Lumia    |  200.00 | 500.0000000000000000 | 200.0000000000000000 |      200.00 |     900.00Smartphone |          2 | HTC One            |  400.00 | 500.0000000000000000 | 300.0000000000000000 |      200.00 |     900.00Smartphone |          3 | Nexus              |  500.00 | 500.0000000000000000 | 366.6666666666666667 |      200.00 |     900.00Smartphone |          4 | iPhone             |  900.00 | 500.0000000000000000 | 500.0000000000000000 |      200.00 |     900.00Tablet     |         10 | Kindle Fire        |  150.00 | 350.0000000000000000 | 150.0000000000000000 |      150.00 |     700.00Tablet     |         11 | Samsung Galaxy Tab |  200.00 | 350.0000000000000000 | 175.0000000000000000 |      150.00 |     700.00Tablet     |          9 | iPad               |  700.00 | 350.0000000000000000 | 350.0000000000000000 |      150.00 |     700.00
(11 行记录)

postgres=# select t1.group_name,t2.product_id,t2.product_name,t2.price,
lag(t2.price,1) over w1 as prev_price,
t2.price-lag(t2.price) over w1 as cur_prev_diff from product_groups t1,products t2 where t1.group_id=t2.group_id 
window w1 as (partition by t1.group_name order by t2.price);group_name | product_id |    product_name    |  price  | prev_price | cur_prev_diff
------------+------------+--------------------+---------+------------+---------------Laptop     |          7 | Sony VAIO          |  700.00 |            |Laptop     |          6 | Lenovo Thinkpad    |  700.00 |     700.00 |          0.00Laptop     |          8 | Dell Vostro        |  800.00 |     700.00 |        100.00Laptop     |          5 | HP Elite           | 1200.00 |     800.00 |        400.00Smartphone |          1 | Microsoft Lumia    |  200.00 |            |Smartphone |          2 | HTC One            |  400.00 |     200.00 |        200.00Smartphone |          3 | Nexus              |  500.00 |     400.00 |        100.00Smartphone |          4 | iPhone             |  900.00 |     500.00 |        400.00Tablet     |         10 | Kindle Fire        |  150.00 |            |Tablet     |         11 | Samsung Galaxy Tab |  200.00 |     150.00 |         50.00Tablet     |          9 | iPad               |  700.00 |     200.00 |        500.00
(11 行记录)