如何显示每个月的总利润，当oracle中当月没有记录时显示null

Question

我正在制作一份报告以显示 2018 年每个月的总利润，并在某些月份没有赚取利润时显示 NIL

赚取的利润 = 0.1 * Total_payment。 服务完成后赚取利润，“Total_payment”列来自表BOOKING，我必须加入BOOKING和SERVICE才能获得每个月的总利润，Booking_num是加入BOOKING和SERVICE的关键， Actual_end 是服务的结束日期

现在的问题是 1 月、2 月和 8 月没有赚取利润。 无论如何，这三个月的利润栏中是否显示 NIL？

SELECT EXTRACT(MONTH FROM Actual_end) AS MONTH,SUM(Total_payment *0.1) AS PROFIT
FROM SERVICE,BOOKING
WHERE SERVICE.Booking_num = BOOKING.Booking_num
AND EXTRACT(YEAR FROM Actual_end) = 2018
GROUP BY EXTRACT(MONTH FROM Actual_end);

这是显示9个月利润的代码，没有一月，二月和八月

MONTH  PROFIT
3      88.4
4      146.1
5      112.6
6      108.3
7      102.6
9      130.3
10     72.6
12     124.9

我希望输出是

MONTH    PROFIT
1        NIL
2        NIL
3        88.4
4        146.1 
5        112.6
6        108.3
7        102.6
8        NIL
9        130.3
10       72.6
11       124.9
12       25.2

怎么修改，我也试过了

WITH CALENDAR AS(
SELECT TO_CHAR(add_months(date '2018-01-01',ROWNUM -1),'MM') AS MONTH
FROM DUAL
CONNECT BY LEVEL <=12)
SELECT CALENDER.MONTH, NVL(SUM(Total_payment*0.1),null) AS PROFIT
FROM BOOKING,SERVICE,CALENDER
WHERE BOOKING.Booking_num = SERVICE.Booking_num
AND CALENDER.MONTH = EXTRACT(MONTH FROM Actual_end(+))
AND EXTRACT(MONTH FROM Actual_end) = 2018
GROUP BY CALENDER.MONTH

输出： 未选择任何行

Answer 1

你需要和外连接（左或右）。顺便说一句，摆脱老式的逗号分隔表之间的连接，而是使用显式连接。

如果返回某一年和整月是问题，请将RIGHT JOIN (SELECT LEVEL AS MNT FROM DUAL CONNECT BY LEVEL <= 12 ) MNT 添加到您的查询中：

SELECT MNT AS MONTH,NVL(TO_CHAR(SUM(Total_payment *0.1)),'NIL') AS PROFIT
  FROM SERVICE S
  JOIN BOOKING B
    ON S.Booking_num = B.Booking_num
 RIGHT JOIN (SELECT LEVEL AS MNT 
               FROM DUAL 
             CONNECT BY LEVEL <= 12 ) MNT
         ON MNT.MNT = EXTRACT(MONTH FROM Actual_end) 
           AND EXTRACT(YEAR FROM Actual_end)=2018                     
GROUP BY MNT
ORDER BY MONTH;

Demo

Answer 2

在这种情况下，您需要一个所有月份的列表：

with months as (
      select 1 as month from dual union all
      select 2 as month from dual union all
      select 3 as month from dual union all
      select 4 as month from dual union all
      select 5 as month from dual union all
      select 6 as month from dual union all
      select 7 as month from dual union all
      select 8 as month from dual union all
      select 9 as month from dual union all
      select 10 as month from dual union all
      select 11 as month from dual union all
      select 12 as month from dual
     )
select m.month, sum(s.total_payment * 0.1) as profit
from months m left join
     booking b
     on extract(month from b.actual_end) = m.month and
        b.actual_end >= date '2018-01-01' and
        b.actual_end < date '2019-01-01' left join
     service s join
     on s.booking_num = b.booking_num 
group by m.month;

注意：

• 这是在猜测actual_end 在booking 中，而total_payment 在service 中。如果这个猜测不正确，查询会略有不同。
• 切勿在FROM 子句中使用逗号。
• 此查询应使用LEFT JOIN。第一个表包含您想要的所有行。
• 后续表的过滤器放在on 子句中，而不是where 子句中。
• 注意日期常量的使用。这种比较通常使引擎更容易优化查询（通常通过使用索引）。