大约tablefunc
和crosstab
的TIL。起初,我想“按列对数据进行分组”,但这实际上没有任何意义。
我的产品销售情况如下
product_id | units | date
-----------------------------------
10 | 1 | 1-1-2018
10 | 2 | 2-2-2018
11 | 3 | 1-1-2018
11 | 10 | 1-2-2018
12 | 1 | 2-1-2018
13 | 10 | 1-1-2018
13 | 10 | 2-2-2018
我想生成一个以月为列的产品表
product_id | 01-01-2018 | 02-01-2018 | etc.
-----------------------------------
10 | 1 | 2
11 | 13 | 0
12 | 0 | 1
13 | 20 | 0
首先,我将按月份分组,然后对产品进行反转和分组,但是我不知道该怎么做。
答案 0 :(得分:1)
在enabling the tablefunc extension之后,
SELECT product_id, coalesce("2018-1-1", 0) as "2018-1-1"
, coalesce("2018-2-1", 0) as "2018-2-1"
FROM crosstab(
$$SELECT product_id, date_trunc('month', date)::date as month, sum(units) as units
FROM test
GROUP BY product_id, month
ORDER BY 1$$
, $$VALUES ('2018-1-1'::date), ('2018-2-1')$$
) AS ct (product_id int, "2018-1-1" int, "2018-2-1" int);
收益
| product_id | 2018-1-1 | 2018-2-1 |
|------------+----------+----------|
| 10 | 1 | 2 |
| 11 | 13 | 0 |
| 12 | 0 | 1 |
| 13 | 10 | 10 |