我有一些名为分类的表,其中包含 classification_indicator_id
。
我需要对这个 ID
求和并放入 1 天的系列。
我需要添加大约 20 列(使用另一个 classification_indicator_id
)。
我修改了一点来自 previous question 的答案:
select
data.d::date as "data",
sum(c.classification_indicator_id)::integer as "Segment1",
sum(c4.classification_indicator_id)::integer as "Segment2",
sum(c5.classification_indicator_id)::integer as "Segment3"
from
generate_series(
'2013-03-25'::timestamp without time zone,
'2013-04-01'::timestamp without time zone,
'1 day'::interval
) data(d)
left join classifications c on (data.d::date = c.created::date and c.classification_indicator_id = 3)
left join classifications c4 on (data.d::date = c4.created::date and c4.classification_indicator_id = 4)
left join classifications c5 on (data.d::date = c5.created::date and c5.classification_indicator_id = 5)
group by "data"
ORDER BY "data"
但仍然无法正常工作。每行的 sum
太大,并且在我添加额外的列时增长。在 segment1
中有 4 列的第二个表中,2013-03-26 的数量应该与第一个表等中的数量相同。
With 3 column With 4 columns
data | Segment1 | Segment2 data | Segment1 | Segment2 | Segment3
-------------------------------- -------------------------------------------
2013-03-25 | 12 | 16 2013-03-25 | 12 | 16 | 20
-------------------------------- -------------------------------------------
2013-03-26 | 18 | 24 2013-03-26 | 108 | 144 | 180
最佳答案
作为commented under your previous answer ,您遇到了“代理交叉连接”。
我在这个相关答案中更详细地解释了它:
Two SQL LEFT JOINS produce incorrect result
你的查询应该是这样的:
SELECT d.created AS data
,c3.segment1
,c4.segment2
,c5.segment3
FROM (
SELECT generate_series('2013-03-25'::date
,'2013-04-01'::date
,interval '1 day')::date AS created
) d
LEFT JOIN (
SELECT created
,sum(classification_indicator_id)::integer AS segment1
FROM classifications
WHERE classification_indicator_id = 3
GROUP BY 1
) c3 USING (created)
LEFT JOIN (
SELECT created
,sum(classification_indicator_id)::integer AS segment2
FROM classifications
WHERE classification_indicator_id = 4
GROUP BY 1
) c4 USING (created)
LEFT JOIN (
SELECT created
,sum(classification_indicator_id)::integer AS segment3
FROM classifications
WHERE classification_indicator_id = 5
GROUP BY 1
) c5 USING (created)
ORDER BY 1;
假设 created
是一个 date
,而不是 timestamp
。
或者,为了更快的查询,因为这已经成为一个话题:
SELECT d.created AS data
,count(classification_indicator_id = 3 OR NULL)::int * 3 AS segment1
,count(classification_indicator_id = 4 OR NULL)::int * 4 AS segment2
,count(classification_indicator_id = 5 OR NULL)::int * 5 AS segment3
FROM (
SELECT generate_series('2013-03-25'::date
,'2013-04-01'::date
,interval '1 day')::date AS created
) d
LEFT JOIN classifications c USING (created)
GROUP BY 1
ORDER BY 1;
关于sql - generate_series() 在 PostgreSQL 中无法按预期方式使用 sum,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/15811735/