过滤所有两个表以获取所有数据

Question

我为调查软件创建了一个数据库。数据库的两个表是我想要做的，我想从两个日期范围和某个位置获取平均分数，并获得没有答案的零或为零或零。我尝试了

SELECT
    AVG(tbAnswers.averageScore)
FROM
    tbDrivers
LEFT JOIN tbAnswers ON tbDrivers.driverId = tbAnswers.driverId
WHERE
    tbDrivers.place = 'WDC'
GROUP BY
    tbDrivers.driverId 

但是当我指定日期范围时，没有答案就无法获取驱动程序的数据。

SELECT AVG(tbAnswers.averageScore)
FROM tbDrivers LEFT JOIN tbAnswers ON tbDrivers.driverId = tbAnswers.driverId
WHERE tbDrivers.place = 'WDC'
      AND answerDate BETWEEN '2018-11-28' AND '2018-12-03'
GROUP BY tbDrivers.driverId

表结构：

CREATE TABLE `tbAnswers` (
  `answerId` int(11) NOT NULL,
  `answerDate` date NOT NULL,
  `driverId` int(11) NOT NULL,
  `score1` int(11) NOT NULL,
  `score2` int(11) NOT NULL,
  `score3` int(11) NOT NULL,
  `averageScore` float NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

INSERT INTO `tbAnswers` (`answerId`, `answerDate`, `driverId`, `score1`, `score2`, `score3`, `averageScore`) VALUES
(10, '2018-11-28', 1032, 0, 0, 0, 0),
(11, '2018-11-29', 1032, 9, 8, 3, 6.67),
(12, '2018-11-30', 1032, 0, 3, 2, 1.67),
(13, '2018-11-30', 1035, 10, 2, 10, 7.34),
(14, '2018-11-01', 1032, 5, 5, 5, 5),
(15, '2018-12-03', 1035, 5, 5, 7, 5.67);

CREATE TABLE `tbDrivers` (
  `driverId` int(11) NOT NULL,
  `nameSurname` varchar(32) NOT NULL,
  `place` varchar(64) NOT NULL,
  `plate` varchar(8) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

INSERT INTO `tbDrivers` (`driverId`, `nameSurname`, `place`, `plate`) VALUES
(1032, 'Nick Oliver', 'WDC', 'B16186D'),
(1033, 'Nicholas Keller', 'WDC', 'ACG8095'),
(1034, 'Felipe Mendez', 'WDC', 'C26106E'),
(1035, 'Lowell Butler', 'WDC', '5123QK');

我该如何解决这个问题？

Answer 1

使用查询来获取至少有一个答案的驱动程序，UNION没有答案的驱动程序：

(SELECT tbDrivers.driverId, AVG(tbAnswers.averageScore) AS avgscore
FROM tbDrivers LEFT JOIN tbAnswers ON tbDrivers.driverId = tbAnswers.driverId
WHERE tbDrivers.place = 'WDC'
      AND answerDate BETWEEN '2018-11-28' AND '2018-12-03'
GROUP BY tbDrivers.driverId )
UNION 
(SELECT t.driverId,  NULL AS avgscore
FROM tbDrivers t
WHERE
      NOT EXISTS (SELECT 1 FROM tbAnswers WHERE tbAnswers.driverId = t.driverId))
ORDER BY driverId

结果是：

driverId    avgscore
1032        2.7800000111262
1033        (null)
1034        (null)
1035        6.505000114440918

Answer 2

出现问题是因为在tbanswers表中没有关于driverid的记录。

要么在tbanswers中输入条目，要么使用上面Forpas给出的查询或使用该查询

SELECT tbdrivers.driverid, 
       Avg(tbanswers.averagescore) 
FROM   tbdrivers 
       LEFT JOIN tbanswers 
              ON tbdrivers.driverid = tbanswers.driverid 
WHERE  tbdrivers.place = 'WDC' 
       AND answerdate BETWEEN '2018-11-28' AND '2018-12-03' 
        OR answerdate IS NULL 
GROUP  BY tbdrivers.driverid