SQL语法练习

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  1. 查询学习课程”python”比课程 “java” 成绩高的学生的学号;
    – 思路：
    – 获取所有有python课程的人（学号，成绩） - 临时表
    – 获取所有有java课程的人（学号，成绩） - 临时表
    – 根据学号连接两个临时表：
    – 学号 | 物理成绩 | 生物成绩
    – 然后再进行筛选
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    select A.s_id from
    		(select s_id, num as python from score left join course on score.c_id = course.c_id where course.c_name = 'python') as A
    		left join
    		(select s_id, num as java   from score left join course on score.c_id = course.c_id where course.c_name = 'java')   as B
    		on A.s_id = B.s_id where A.python > B.java;

  1. 查询平均成绩大于65分的同学的姓名和平均成绩(保留两位小数);

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    SELECT student.s_name as names, round(AVG(score.num), 2) as average
    FROM student, score
    WHERE student.s_id = score.s_id
    GROUP BY student.s_name
    HAVING AVG(score.num) > 65;

  2. 查询所有同学的姓名、选课数、总成绩

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    SELECT student.s_name, COUNT(score.s_id) as course_num, SUM(score.num) as total_grades
    FROM student, score
    WHERE student.s_id = score.s_id
    GROUP BY student.s_name
    ORDER BY student.s_name;

  3. 查询所有的课程的名称以及对应的任课老师姓名;

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    SELECT course.c_name, teacher.t_name  
    FROM course, teacher
    WHERE course.t_id = teacher.t_id;

  4. 查询没学过“alex”老师课的同学的姓名;

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    SELECT s_name
    FROM student
    WHERE student.s_id NOT IN (
    			SELECT DISTINCT score.s_id
    			FROM score, course, teacher
    			WHERE course.c_id = score.c_id AND teacher.t_id = course.t_id AND teacher.t_name = 'alex'
    			)

  5. 查询学过’python’并且也学过编号’java’课程的同学的姓名

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    SELECT s_name FROM
    		(SELECT score.s_id as sid, score.c_id as cid
    		 FROM score, course
    		 WHERE score.c_id = course.c_id AND (course.c_name = 'python' OR course.c_name = 'java')) as B
    LEFT JOIN student ON B.sid = student.s_id
    GROUP BY s_name
    HAVING COUNT(s_name) > 1;

  6. 查询学过“alex”老师所教的全部课程的同学的姓名

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    SELECT s_name FROM
    		(SELECT score.s_id as sid, score.c_id as cid
    		 FROM score, course, teacher
    		 WHERE score.c_id = course.c_id AND teacher.t_id = course.t_id AND teacher.t_name = 'alex') as B
        LEFT JOIN student ON B.sid = student.s_id
    GROUP BY s_name
    HAVING COUNT(s_name) = (SELECT COUNT(course.c_id) FROM
    												course, teacher
    												WHERE
    												teacher.t_id = course.t_id AND teacher.t_name='alex');

  7. 查询挂科超过两门(包括两门)的学生姓名;

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    SELECT s_name FROM
    		(SELECT score.s_id as sid, score.c_id as大专栏  SQL语法练习(一)span> cid
    		 FROM score, course
    		 WHERE score.c_id = course.c_id  AND (score.num < 60 OR score.num ISNULL)) as B
         LEFT JOIN student ON B.sid = student.s_id
    GROUP BY s_name
    HAVING COUNT(s_name) > 1;

  8. 查询有课程成绩小于60分的同学的姓名;

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    SELECT s_name FROM
    		(SELECT score.s_id as sid, score.c_id as cid
    		 FROM score, course
    		 WHERE score.c_id = course.c_id  AND score.num < 60) as B
         LEFT JOIN student ON B.sid = student.s_id
    GROUP BY s_name;

  9. 查询选修了全部课程的学生姓名;

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    SELECT s_name FROM
    		(SELECT score.s_id as sid, score.c_id as cid
    		 FROM score, course
    		 WHERE score.c_id = course.c_id) as B
         LEFT JOIN student ON B.sid = student.s_id
    GROUP BY s_name
    HAVING COUNT(s_name) = (SELECT COUNT(*) FROM course);


    SELECT s_name FROM
    student
    LEFT JOIN score ON student.s_id = score.s_id
    GROUP BY s_name
    HAVING COUNT(s_name) = (SELECT COUNT(*) FROM course)

  10. 查询至少有一门课程与“貂蝉”同学所学课程相同的同学姓名；

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    SELECT s_name
    FROM student, score
    WHERE student.s_id = score.s_id AND student.s_name != '貂蝉' AND score.c_id IN (SELECT c_id FROM score, student
    																									 WHERE score.s_id = student.s_id AND student.s_name = '貂蝉')

    GROUP BY s_name;

  11. 查询学过’貂蝉’同学全部课程的其他同学姓名；

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    SELECT s_name FROM
    		(SELECT score.s_id as sid, score.c_id as cid
    		 FROM score, course, student
    		 WHERE
    		     score.c_id = course.c_id AND
    				 student.s_id = score.s_id AND
    				 student.s_name != '貂蝉' AND
    				 score.c_id in (SELECT c_id FROM score, student WHERE student.s_name = '貂蝉' AND student.s_id = score.s_id)
    		) as B
    LEFT JOIN student ON B.sid = student.s_id
    GROUP BY s_name
    HAVING COUNT(s_name) >= (SELECT COUNT(score.c_id) FROM score, student WHERE student.s_name = '貂蝉' AND student.s_id = score.s_id);

– ——————————————————————————————————————————————————————————————
– INSERT INTO student VALUES (1, ‘鲁班’, 12, ‘男’);
– INSERT INTO student VALUES (2, ‘貂蝉’, 20, ‘女’);
– INSERT INTO student VALUES (3, ‘刘备’, 35, ‘男’);
– INSERT INTO student VALUES (4, ‘关羽’, 34, ‘男’);

– INSERT INTO student VALUES (5, ‘张飞’, 33, ‘女’);

–

–
– INSERT INTO teacher VALUES (1, ‘大王’);
– INSERT INTO teacher VALUES (2, ‘alex’);
– INSERT INTO teacher VALUES (3, ‘egon’);

– INSERT INTO teacher VALUES (4, ‘peiqi’);

– INSERT INTO course VALUES (1, ‘python’, 1);
– INSERT INTO course VALUES (2, ‘java’, 2);
– INSERT INTO course VALUES (3, ‘linux’, 3);
– INSERT INTO course VALUES (4, ‘go’, 2);

– INSERT INTO score VALUES (1, 1, 1, 79);
– INSERT INTO score VALUES (2, 1, 2, 77);
– INSERT INTO score VALUES (3, 1, 3, 58);
– INSERT INTO score VALUES (4, 2, 2, 66);
– INSERT INTO score VALUES (5, 2, 3, 77);
– INSERT INTO score VALUES (6, 3, 1, 61);
– INSERT INTO score VALUES (7, 3, 2, 64);

– INSERT INTO score VALUES (8, 4, 3, 70);

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