将3列总和合并为一个表

Question

我有一个简单的数据库来模拟电影租赁服务.我有以下3个选择查询,它们可以自行完成:

1. 计算租赁价格的所有收入:

   SELECT SUM(PRICE) AS RENTAL_REVENUE
       FROM RENTAL
   

   输出:

       +----------------+
       | RENTAL_REVENUE |
       +----------------+
       |      39.92     |
       +----------------+
   

2. 计算支付滞纳金的所有收入:

   SELECT SUM(NULLIF(LATEFEE, 0)) AS PAID_LATE_FEES
       FROM RENTAL
       WHERE RETURNED = 1
   

   输出:

       +----------------+
       | PAID_LATE_FEES |
       +----------------+
       |       2.99     |
       +----------------+
   

3. 计算所有尚未支付的滞纳金的总和:

   SELECT SUM(NULLIF(LATEFEE, 0)) AS OUTSTANDING_LATE_FEES
       FROM RENTAL
       WHERE RETURNED = 0
   

   输出:

       +-----------------------+
       | OUTSTANDING_LATE_FEES |
       +-----------------------+
       |          5.98         |
       +-----------------------+
   

我想将这3个查询的结果合并到一个包含3列的表中,如下所示:

+----------------+----------------+-----------------------+
| RENTAL_REVENUE | PAID_LATE_FEES | OUTSTANDING_LATE_FEES |
+----------------+----------------+-----------------------+
|      39.92     |       2.99     |          5.98         |
+----------------+----------------+-----------------------+

我能够通过以下查询实现这一点,但1 = 1废话告诉我可能有更好的方法.

SELECT rental_revenue + paid_late_fees + outstanding_late_fees AS TOTAL_REVENUE, 
       rental_revenue, 
       paid_late_fees, 
       outstanding_late_fees 
FROM   (SELECT SUM(price) AS RENTAL_REVENUE 
        FROM   rental) 
       inner join (SELECT SUM(Nullif(latefee, 0)) AS PAID_LATE_FEES 
                   FROM   rental 
                   WHERE  returned = 1) 
               ON 1 = 1 
       inner join (SELECT SUM(Nullif(latefee, 0)) AS OUTSTANDING_LATE_FEES 
                   FROM   rental 
                   WHERE  returned = 0) 
               ON 1 = 1;

有没有更好的办法？

Answer 1

您可以选择所有记录并在SUM使用中构建过滤器CASE-WHEN或DECODE:

SELECT SUM(price) AS rental_revenue,
       SUM(CASE 
             WHEN returned = 1 AND latefee <> 0 THEN latefee
             ELSE 0
           END) AS paid_late_fees,
       SUM(CASE
             WHEN returned = 0 AND latefee <> 0 THEN latefee
             ELSE 0
           END) AS outstanding_late_fees             
FROM rental