如何查询月份和工作日？

Question

我有一个查询，我正在做这样的事情

 query =
  from(
    u in User,
    where: u.user_id == ^user_id,
    group_by: [
      fragment("date_part(?,?)::int", "month", u.inserted_at),
      u.user_id
    ],
    select: %{
      month: fragment("date_part(?,?)::int", "month", u.inserted_at),
      weekly: filter(count(u.user_id), fragment("date_trunc('week', ?) = date_trunc('week', current_timestamp)", u.inserted_at)),
      monthly: count(u.user_id),
    }
  )

我试图得到一个结果，我想知道每个月有多少用户插入，工作日和周末有多少用户？

结果会是这样的

[
  %{month: 10, users: 5, weekday: 2, weekend: 3},
  %{month: 9, users: 5, weekday: 1, weekend: 4}
]

在这之后我不知道如何继续，请给我一些建议

Answer 1

只是一些 PostgreSQL 方言中的 SQL 语句。

SELECT
  date_part('year', users.inserted_at) AS year,  -- remove this line if you think January 2020 and January 2021 are the same month.
  date_part('month', users.inserted_at) AS month,
  date_part('isodow', users.inserted_at) >= 6 AS weekend,
  COUNT(users.id) AS "count"
FROM
  users
GROUP BY
  year,  -- remove this line if you think January 2020 and January 2021 are the same month.
  month,
  weekend
ORDER BY
  year ASC,  -- remove this line if you think January 2020 and January 2021 are the same month.
  month ASC,
  weekend ASC

您无法仅通过 SQL 查询获得所需的答案，因为 users 和 weekend/weekday 的聚合具有不同的粒度。您必须在 RAM 中进行一些计算。