Question

我有以下架构： http://sqlfiddle.com/#!9/bd3a4/1 我想要按日期分组（）并添加user_id =？每天计算每天的结果。必填结果日| TotalRequests | TotalOrders

Answer 1

由于您可以在第1天订购，并在第8天收到请求，因此您可能在一侧有条目而在另一侧没有。为了满足您的需求，我会按日期单独处理所有订单和请求的UNION。然后将这些值向上滚动。内部Pre-Aggregate结果查询是应用每个用户的WHERE子句的位置。预聚合查询还有一个recSource列，用于指示记录来自订单的“O”和来自请求的“R”，因此汇总知道分别存储总计数的列。

select
      preAgg.recDate,
      SUM( case when preAgg.recSource = 'O' then preAgg.recCount else 0 end ) as OrderCount,
      SUM( case when preAgg.recSource = 'R' then preAgg.recCount else 0 end ) as RequestCount
   from
      ( select
              date(o.created_at) recDate,
              'O' as recSource,
              count(*) as recCount
           from
              orders o
           where
              o.user_id = 3
           group by
              date(o.created_at)
       UNION ALL
       select
              date(r.created_at) recDate,
              'R' as recSource,
              count(*) as recCount
           from
              requests r
           where
              r.user_id = 3
           group by
              date(r.created_at) ) preAgg
   group by
      preAgg.recDate
   order by 
      preAgg.recDate

对于查询优化，我会确保您的订单和请求表都有一个索引（user_id，created_at）。

SQL Fiddle result

Answer 2

您可以使用以下查询：

SELECT
DATE(o.created_at) AS Day
,COUNT(r.id) AS TotalRequests
,COUNT(o.id) AS TotalOrders 
FROM orders o
LEFT JOIN
requests r ON
r.id = o.request_id
WHERE o.user_id = 3
GROUP BY DATE(r.created_at), DATE(o.created_at),o.user_id

如何将mysql按日期分组多次左连接

2 个答案: