Question

[

SELECT r.AdNo,
       r.Name,
       SUM(CASE WHEN p.SubjectID = 101 THEN s.score ELSE 0 END) AS ENGLISH,
       SUM(CASE WHEN p.SubjectID = 102 THEN s.score ELSE 0 END) AS KISWAHILI,
       SUM(CASE WHEN p.SubjectID = 103 THEN s.score ELSE 0 END) AS MATH,
       SUM(CASE WHEN p.SubjectID = 104 THEN s.score ELSE 0 END) AS CRE,
       SUM(CASE WHEN p.SubjectID = 105 THEN s.score ELSE 0 END) AS 'SOCIAL STUDIES',
       SUM(CASE WHEN p.SubjectID THEN s.score ELSE 0 END) AS 'TOTAL',
       (sum(s.score)/count(s.SubjectID) ) AS 'AVERAGE',
       g.grade_letter
  FROM student r
       INNER JOIN marks s ON r.AdNo = s.AdNo
       INNER JOIN subject p ON s.SubjectID = p.SubjectID
       INNER JOIN grades g ON 77.2 BETWEEN g.lowerlimit AND g.upperlimit
  GROUP BY r.Name
  order by AVERAGE DESC;

[SET FOREIGN_KEY_CHECKS=0;

-- ----------------------------
-- Table structure for category
-- ----------------------------
DROP TABLE IF EXISTS `category`;
CREATE TABLE `category` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `CategoryID` int(4) NOT NULL,
  `CategoryName` varchar(20) NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `CategoryID` (`CategoryID`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=latin1;

-- ----------------------------
-- Table structure for grades
-- ----------------------------
DROP TABLE IF EXISTS `grades`;
CREATE TABLE `grades` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `grade_letter` char(2) DEFAULT NULL,
  `lowerlimit` double DEFAULT NULL,
  `upperlimit` double DEFAULT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `grade_letter` (`grade_letter`)
) ENGINE=InnoDB AUTO_INCREMENT=28 DEFAULT CHARSET=latin1;

-- ----------------------------
-- Table structure for marks
-- ----------------------------
DROP TABLE IF EXISTS `marks`;
CREATE TABLE `marks` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `AdNo` varchar(10) DEFAULT NULL,
  `SubjectID` int(3) DEFAULT NULL,
  `score` double DEFAULT NULL,
  `CategoryID` int(11) NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `AdNo` (`AdNo`,`SubjectID`,`CategoryID`),
  KEY `SubjectID` (`SubjectID`),
  KEY `CategoryID` (`CategoryID`),
  CONSTRAINT `marks_ibfk_1` FOREIGN KEY (`AdNo`) REFERENCES `student` (`AdNo`),
  CONSTRAINT `marks_ibfk_2` FOREIGN KEY (`SubjectID`) REFERENCES `subject` (`SubjectID`),
  CONSTRAINT `marks_ibfk_3` FOREIGN KEY (`CategoryID`) REFERENCES `category` (`CategoryID`)
) ENGINE=InnoDB AUTO_INCREMENT=26 DEFAULT CHARSET=latin1;

-- ----------------------------
-- Table structure for student
-- ----------------------------
DROP TABLE IF EXISTS `student`;
CREATE TABLE `student` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `Name` varchar(30) DEFAULT NULL,
  `AdNo` varchar(10) DEFAULT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `AdNo` (`AdNo`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=latin1;

-- ----------------------------
-- Table structure for subject
-- ----------------------------
DROP TABLE IF EXISTS `subject`;
CREATE TABLE `subject` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `SubjectID` int(3) DEFAULT NULL,
  `SubjectName` varchar(20) DEFAULT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `SubjectID` (`SubjectID`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=latin1;]

Answer 1

而是使A-的上限与A的下限相同，等等。此外，您的成绩表并不能解释平均分数小于1的学生。在这种情况下，我的查询将返回＆＃34; ???＆＃34;等级。

SELECT m.*, COALESCE(grades.grade_letter, '???') AS GRADE
FROM (
    SELECT student.AdNo, student.Name,
           SUM(IF(subject.SubjectID = 101, marks.score, 0)) AS ENGLISH,
           SUM(IF(subject.SubjectID = 102, marks.score, 0)) AS KISWAHILI,
           SUM(IF(subject.SubjectID = 103, marks.score, 0)) AS MATH,
           SUM(IF(subject.SubjectID = 104, marks.score, 0)) AS CRE,
           SUM(IF(subject.SubjectID = 105, marks.score, 0)) AS "SOCIAL STUDIES",
           SUM(IF(subject.SubjectID IS NOT NULL, marks.score, 0)) AS TOTAL,
           SUM(marks.score)/COUNT(*) AS AVERAGE
    FROM student
    INNER JOIN marks ON student.AdNo = marks.AdNo
    INNER JOIN subject ON marks.SubjectID = subject.SubjectID
    GROUP BY student.AdNo
) AS m
LEFT OUTER JOIN grades
    ON m.AVERAGE >= grades.lowerlimit
    AND m.AVERAGE < grades.upperlimit
ORDER BY m.AVERAGE DESC;

为所有科目添加另一名0分的学生，这样做：

+--------+------+---------+-----------+------+------+----------------+-------+---------+-------+
| AdNo   | Name | ENGLISH | KISWAHILI | MATH | CRE  | SOCIAL STUDIES | TOTAL | AVERAGE | GRADE |
+--------+------+---------+-----------+------+------+----------------+-------+---------+-------+
| TU-003 | D K  |      67 |        80 |   90 |   70 |             79 |   386 |    77.2 | A-    |
| TU-004 | G K  |      57 |        76 |   61 |   78 |             80 |   352 |    70.4 | B+    |
| TU-001 | G C  |      67 |        68 |   78 |   54 |             76 |   343 |    68.6 | B+    |
| TU-002 | F K  |      60 |        34 |   74 |   50 |             67 |   285 |      57 | B-    |
| TU-005 | X X  |       0 |         0 |    0 |    0 |              0 |     0 |       0 | ???   |
+--------+------+---------+-----------+------+------+----------------+-------+---------+-------+

我如何根据平均分数进行排名和评分

1 个答案: