Question

我想使用join而不是内联查询，但我能够提供的是给出错误的值。请检查此链接 - http://www.sqlfiddle.com/#!2/57cad/9

它有2个单独的查询，它们提供正确的值和连接查询，结果不正确。

有人可以帮忙......

Answer 1

此处显示的答案：SQLFiddle

您的查询可以在一些区域得到改善，这使得他们的JOIN更加明显。

在第一个查询中，更好的版本具有SELECT子句中列出的GROUP BY子句的列，并且您的HAVING子句（工作时）成为WHERE子句（IMO：最佳做法是仅在HAVING中使用聚合函数子句：）

SELECT usercode, ROUND(coalesce(sum(paymentamount)*0.99,0),2) AS payment 
FROM accountpayments 
WHERE usercode = 21
GROUP BY usercode;

您的第二个查询可以重写为JOIN（与子查询相对）

SELECT campaigns.usercode, ROUND(coalesce(sum(lmc_cds.total_spending),0),2) AS total_spending 
FROM logsmaincontrols_campaigns_daily_stats AS lmc_cds 
JOIN campaigns
  ON campaigns.campcode = lmc_cds.campcode
WHERE campaigns.usercode = 21;

由于查询不共享任何表，我决定使用usercode作为JOINing列将查询作为派生表加入。

SELECT t1.usercode, t1.payment, t2.total_spending
FROM (SELECT usercode, ROUND(coalesce(sum(paymentamount)*0.99,0),2) AS payment 
      FROM accountpayments 
      WHERE usercode = 21
      GROUP BY usercode) AS t1
JOIN (SELECT campaigns.usercode, ROUND(coalesce(sum(lmc_cds.total_spending),0),2) AS total_spending 
      FROM logsmaincontrols_campaigns_daily_stats AS lmc_cds 
      JOIN campaigns
        ON campaigns.campcode = lmc_cds.campcode
      WHERE campaigns.usercode = 21) AS t2
  ON t1.usercode = t2.usercode;

SQL连接查询 - 连接而不是内联查询

1 个答案: