-- 9、检索"01"课程分数小于60，按分数降序排列的学生信息

假设有以下三个表：

-- 学生表
CREATE TABLE `students` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(50) NOT NULL,
  `age` int(11) NOT NULL,
  `gender` varchar(10) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8mb4;

-- 课程表
CREATE TABLE `courses` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(50) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8mb4;

-- 分数表
CREATE TABLE `scores` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `student_id` int(11) NOT NULL,
  `course_id` int(11) NOT NULL,
  `score` int(11) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=utf8mb4;

-- 插入数据
INSERT INTO `students` VALUES (1,'张三',18,'男'),(2,'李四',19,'女'),(3,'王五',20,'男');
INSERT INTO `courses` VALUES (1,'01'),(2,'02');
INSERT INTO `scores` VALUES (1,1,1,80),(2,2,1,70),(3,3,1,59),(4,1,2,90),(5,2,2,75),(6,3,2,85);

则可以使用以下SQL语句查询"01"课程分数小于60，按分数降序排列的学生信息：

SELECT s.id, s.name, c.name AS course, sc.score
FROM students AS s
INNER JOIN scores AS sc ON s.id = sc.student_id
INNER JOIN courses AS c ON sc.course_id = c.id
WHERE c.name = '01' AND sc.score < 60
ORDER BY sc.score DESC;

查询结果为：

+----+------+-------+-------+
| id | name | course| score |
+----+------+-------+-------+
|  3 | 王五 |  01   |  59   |
+----+------+-------+-------+