Question

我一直在使用下面的查询来按月对我进行记录计数。在特定年份效果良好。

但是，如果要比较从2018年1月到2019年1月的计数，会有些痛苦。特别是如果要绘制图形。

我应该如何调整这一点，以便可以通过给出跨度的年数来获得1月18日，2月18日，... 1月19日的结果。

这是Postgres 9.6

谢谢！

SELECT
  count(case when to_char(t.order_date, 'MM') = '01' then 1 END) as Jan,
  count(case when to_char(t.order_date, 'MM') = '02' then 1 END) as Feb,
  count(case when to_char(t.order_date, 'MM') = '03' then 1 END) as Mar,
  count(case when to_char(t.order_date, 'MM') = '04' then 1 END) as Apr,
  count(case when to_char(t.order_date, 'MM') = '05' then 1 END) as May,
  count(case when to_char(t.order_date, 'MM') = '06' then 1 END) as June,
  count(case when to_char(t.order_date, 'MM') = '07' then 1 END) as Jul,
  count(case when to_char(t.order_date, 'MM') = '08' then 1 END) as Aug,
  count(case when to_char(t.order_date, 'MM') = '09' then 1 END) as Sep,
  count(case when to_char(t.order_date, 'MM') = '10' then 1 END) as Oct,
  count(case when to_char(t.order_date, 'MM') = '11' then 1 END) as Nov,
  count(case when to_char(t.order_date, 'MM') = '12' then 1 END) as Dec
FROM transactions as t
WHERE to_char(t.order_date, 'YYYY') = '2019'

Answer 1

Please check below query, is this relevant?

Blockquote

选择 to_char（order_date，'YYYY'）， count（to_char（t.order_date，'MM'）='01'然后1 END的情况）为Jan， count（to_char（t.order_date，'MM'）='02'然后1 END的情况）为Feb， count（to_char（t.order_date，'MM'）='03'然后1 END的情况）为Mar， count（to_char（t.order_date，'MM'）='04'然后1 END的情况）为Apr，计数（当to_char（t.order_date，'MM'）='05'然后1 END的情况）为May，计数（当to_char（t.order_date，'MM'）='06'然后1 END的情况）为六月， count（to_char（t.order_date，'MM'）='07'然后1 END的情况）为Jul， count（to_char（t.order_date，'MM'）='08'然后1 END的情况）为Aug，计数（当to_char（t.order_date，'MM'）='09'然后1 END的情况）为Sep， count（to_char（t.order_date，'MM'）='10'然后1 END的情况）为十月， count（to_char（t.order_date，'MM'）='11'然后1 END的情况）为Nov，计数（当to_char（t.order_date，'MM'）='12'然后1 END的情况）为Dec FROM事务作为t（在（'2018'，'2019'）中to_char（order_date，'YYYY'）的地方
按to_char（order_date，'YYYY'）分组；

Blockquote

Answer 2

您可以通过结合以下方式按时间戳对数据进行“存储桶”操作：

Truncate a timestamp value达到指定的精度，将这些值展平为单个值。
Group by得到的低精度值。

SELECT
    date_trunc('month', t.order_date) AS order_month,
    count(t.order_id) AS count
FROM transaction AS t
GROUP BY order_month
ORDER BY order_month

然后由您决定将结果限制在什么年：

SELECT
    date_trunc('month', t.order_date) AS order_month,
    count(t.order_id) AS count
FROM transaction AS t
WHERE
    date_part('year', t.order_date) = 2019
GROUP BY order_month
ORDER BY order_month

Answer 3

您想要结果在不同的行吗？

SELECT to_char(t.order_date, 'YYYY') = '2019',
       count(*) filter (to_char(t.order_date, 'MM') = '01') as Jan,
       count(*) filter (to_char(t.order_date, 'MM') = '02') as Feb,
       . . .
       count(*) filter (to_char(t.order_date, 'MM') = '12') as Dec
FROM transactions as t
GROUP BY to_char(t.order_date, 'YYYY') = '2019'

SQL查询多个年份中按月计数

3 个答案: