我们如何使用 GROUP BY 加入结果

Posted 2023-03-29

【中文标题】我们如何使用 GROUP BY 加入结果

【英文标题】：How can we join the results with GROUP BY

【发布时间】：2020-01-15 23:44:17

【问题描述】：

我在这里加入三个表，并希望通过方法按组获取结果。当我这样编写查询时

$query=$this->db->query("SELECT p.id, p.customerid, T.u_id, A.u_id, T.agent_name,
       P.date as d_date, T.total_profit, A.t_price, A.t_dc
  FROM bills P
  LEFT JOIN((SELECT *,
                    bill_details.id as b_id,
                    bill_details.user_id as u_id,
                    SUM(bill_details.profit) AS total_profit
               FROM bill_details
              WHERE DATE(bill_details.bill_date) BETWEEN '$start_date' AND
                    '$end_date'
                AND bill_details.user_id = 406
              GROUP BY Date(bill_details.bill_date), bill_details.user_id) T)
    ON p.id = T.bill_id
  LEFT JOIN((SELECT *,
                    assigned_result.assigned_result_id as a_id,
                    assigned_result.user_id as u_id,
                    SUM(assigned_result.total_price) AS t_price,
                    SUM(assigned_result.total_dc) AS t_dc
               FROM assigned_result
              WHERE DATE(assigned_result.date) BETWEEN '$start_date' AND
                    '$end_date'
                AND assigned_result.user_id = 406
              GROUP BY Date(assigned_result.date), assigned_result.user_id) A)
    ON p.id = A.bill_no
 WHERE T.u_id = 406
    OR A.u_id = 406");
  return $query->result();

如果我在做这样的 group_by 条件GROUP BY T.u_id,A.u_id 我的输出看起来像这样

Name    Date          Purchase      Winning     Balance

        2019-07-25                    240        -240

Ned     2019-07-25     132.60        0.00         132

我希望结果是这样的

Name    Date          Purchase      Winning     Balance

Ned     2019-07-25    132.60          240          132

【参考方案1】：

使用额外的max() 聚合：

SELECT max(Name) as Name, Date, max(Purchase) as Purchase, 
       max(Winning) as Winning, max(Balance) as Balance
  FROM
  (
   <YourOriginalQuery>
  ) q
 GROUP BY Date;

【参考方案2】：

您没有使用GROUP BY 显示查询。但是根据您的描述，您可以执行以下任一操作：

完全删除GROUP BY。聚合查询将返回一行。 使用 `GROUP BY COALESCE(T.u_id, A.u_id)

如果这些列在SELECT 中，您可能还需要调整SELECT 子句。