Question

在我的一个应用程序中，我需要计算燃料消耗，考虑到完全的加油和部分加油。我的Android应用程序基于SQLite语法和功能。

我尝试在SQL中解决这个难题，并且不希望通过所有行来以编程方式执行此操作。

FULL ='N'的行应该在结果列表中省略，但是它们的值应该添加到下一个FULL ='Y'行。至少这是我的想法。

这是DML（仅显示所需的列）：

CREATE TABLE FUELINGS (
ID INTEGER PRIMARY KEY,
MILEAGE INTEGER,
VOLUME DECIMAL(8, 2),
FULL CHAR(1));

以下是此表的一些输入：

INSERT INTO FUELINGS VALUES(1,22995,29.48,'Y');
INSERT INTO FUELINGS VALUES(2,23385,31.27,'Y');
INSERT INTO FUELINGS VALUES(3,23869,16.71,'N');
INSERT INTO FUELINGS VALUES(4,24065,33.18,'Y');
INSERT INTO FUELINGS VALUES(5,24485,30.59,'Y');
INSERT INTO FUELINGS VALUES(6,24956,33.78,'Y');

好的，这就是问题所在。这是我使用的查询：

SELECT T2.MILEAGE, 
       T2.VOLUME, 
       T2.FULL, 
       T2.PREVMILEAGE, 
       T2.PREVVOLUME, 
       T2.PREVFULL, 
       100 * T2.VOLUME / ( T2.MILEAGE - T2.PREVMILEAGE ) 
FROM   (SELECT T.MILEAGE, 
               T.VOLUME, 
               T.FULL, 
               T.PREVMILEAGE, 
               (SELECT VOLUME 
                FROM   FUELINGS 
                WHERE  MILEAGE = T.PREVMILEAGE 
                       AND MILEAGE IS NOT NULL 
                       AND MILEAGE > 0 
                       AND VOLUME IS NOT NULL 
                       AND VOLUME > 0) AS PREVVOLUME, 
               (SELECT FULL 
                FROM   FUELINGS 
                WHERE  MILEAGE = T.PREVMILEAGE 
                       AND MILEAGE IS NOT NULL 
                       AND MILEAGE > 0 
                       AND VOLUME IS NOT NULL 
                       AND VOLUME > 0) AS PREVFULL 
        FROM   (SELECT F.MILEAGE, 
                       F.VOLUME, 
                       F.FULL, 
                       (SELECT Max(MILEAGE) 
                        FROM   FUELINGS PREV 
                        WHERE  PREV.MILEAGE < F.MILEAGE 
                               AND MILEAGE IS NOT NULL 
                               AND MILEAGE > 0 
                               AND VOLUME IS NOT NULL 
                               AND VOLUME > 0) AS PREVMILEAGE 
                FROM   FUELINGS F 
                WHERE  MILEAGE IS NOT NULL 
                       AND MILEAGE > 0 
                       AND VOLUME IS NOT NULL 
                       AND VOLUME > 0) AS T 
        WHERE  PREVMILEAGE IS NOT NULL) AS T2 
ORDER  BY T2.MILEAGE;

结果如下：

T2.MILEAGE  T2.VOLUME   T2.FULL T2.PREVMILEAGE  T2.PREVVOLUME   T2.PREVFULL 100 * T2.VOLUME / (T2.MILEAGE - T2.PREVMILEAGE)
23385   31.27   Y   22995   29.48   Y   8.017948717948718
23869   16.71   N   23385   31.27   Y   3.4524793388429753
24065   33.18   Y   23869   16.71   N   16.928571428571427
24485   30.59   Y   24065   33.18   Y   7.283333333333333
24956   33.78   Y   24485   30.59   Y   7.171974522292993

16.92是错误的，因为在那之前加油是部分加油。我需要求和并计算两行。我知道可能有一个以上的部分加油。但我没有任何线索如何构建FULL ='N'值的范围，将它们相加并将它们添加到下面的FULL ='Y'值。

可以请有人把我放在正确的方向。我怎样才能做到这一点？

非常感谢提前。

修改/溶液

SELECT T.MILEAGE,
       T.PREVMILEAGE,
       SUM(VOLUME),
       100 * SUM(VOLUME) / ( T.MILEAGE - T.PREVMILEAGE )
FROM   (SELECT F1.MILEAGE      AS MILEAGE,
               MAX(F2.MILEAGE) AS PREVMILEAGE
        FROM   FUELINGS F1
               LEFT OUTER JOIN FUELINGS F2
                 ON F1.MILEAGE > F2.MILEAGE
                    AND F2.FULL = 'Y'
                    AND F2.MILEAGE IS NOT NULL
                    AND F2.MILEAGE > 0
                    AND F2.VOLUME IS NOT NULL
                    AND F2.VOLUME > 0.0
        WHERE  F1.FULL = 'Y'
               AND F1.MILEAGE IS NOT NULL
               AND F1.MILEAGE > 0
               AND F1.VOLUME IS NOT NULL
               AND F1.VOLUME > 0.0
        GROUP  BY F1.MILEAGE) AS T,
       (SELECT VOLUME
        FROM   FUELINGS F3
        WHERE  F3.MILEAGE > T.PREVMILEAGE
               AND F3.MILEAGE <= T.MILEAGE)
GROUP  BY T.MILEAGE

Answer 1

如果您有一个名为FuelingsFull的表，您的原始查询将起作用，该表仅包含有关完全加油的完整信息。这可以从Fueling中总结出来。使用窗口函数的过程会更简单，但是你没有SQLite中的那些。

所以，这里有一个关于如何做到这一点的想法。首先，获取之前的完整ID：

select f1.id, max(f2.full) as prevFullId
from fuelings f1 left outer join
     fuelings f2
     on f1.id > f2.id and
        f2.full = 0
group by f1.id

现在，你有一组所有属于一起的燃料。下一个查询将这个加入到燃料中，然后将它们组合在一起。

select fills.id, max(mileage) as mileage, sum(volume) as volume, count(*) as numFills
from fuelings f join
     (select f1.id, max(f2.full) as prevFullId
      from fuelings f1 left outer join
           fuelings f2
           on f1.id > f2.id and
              f2.full = 1
      group by f1.id
     ) fills
     on f.id > fills.prevFullId and f.id <= fills.id
  group by fills.id

将此作为您的FuelingFull，原始查询应该有效。

加油计算（全部和部分）

1 个答案: