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2025-02-24 19:34:56 +08:00
parent 7fd11e7618
commit 049a9c4108
1 changed files with 90 additions and 1 deletions
@@ -178,3 +178,92 @@ insert into scores values('07', '03', 98);
 44.查询本月过生日的学生
 45.查询下月过生日的学生
 ```sql
 #1.查询" 01 "课程比" 02 "课程成绩高的学生的信息及课程分数
 SELECT st.*, c1.score '01课程', c2.score '02课程'
 FROM students st, (
 	SELECT sc1.student_id, sc1.score
 	FROM scores sc1
 	WHERE sc1.course_id = 1
 )c1,
 (
 	SELECT sc2.student_id, sc2.score
 	FROM scores sc2
 	WHERE sc2.course_id = 2
 )c2
 WHERE st.id = c1.student_id AND st.id = c2.student_id AND c1.score > c2.score;
 #1.1查询同时存在" 01 "课程和" 02 "课程的情况
 SELECT st.*, c1.score '01课程', c2.score '02课程'
 FROM students st, (
 	SELECT sc1.student_id, sc1.score
 	FROM scores sc1
 	WHERE sc1.course_id = 1
 )c1,
 (
 	SELECT sc2.student_id, sc2.score
 	FROM scores sc2
 	WHERE sc2.course_id = 2
 )c2
 WHERE st.id = c1.student_id AND st.id = c2.student_id;
 #1.2查询存在" 01 "课程但可能不存在" 02 "课程的情况(不存在时显示为 null )
 SELECT st.*, c1.score '01课程', c2.score '02课程'
 FROM students st 
 LEFT JOIN
 (
 	SELECT sc1.student_id, sc1.score
 	FROM scores sc1
 	WHERE sc1.course_id = 1
 )c1 ON st.id = c1.student_id
 LEFT JOIN
 (
 	SELECT sc2.student_id, sc2.score
 	FROM scores sc2
 	WHERE sc2.course_id = 2
 )c2 ON st.id = c2.student_id 
 WHERE c1.score IS NOT NULL;
 #1.3查询不存在" 01 "课程但存在" 02 "课程的情况
 SELECT st.*, c1.score '01课程', c2.score '02课程'
 FROM students st 
 LEFT JOIN
 (
 	SELECT sc1.student_id, sc1.score
 	FROM scores sc1
 	WHERE sc1.course_id = 1
 )c1 ON st.id = c1.student_id
 LEFT JOIN
 (
 	SELECT sc2.student_id, sc2.score
 	FROM scores sc2
 	WHERE sc2.course_id = 2
 )c2 ON st.id = c2.student_id 
 WHERE c1.score IS NULL AND c2.score IS NOT NULL;
 #2.查询平均成绩大于等于 60 分的同学的学生编号和学生姓名和平均成绩
 SELECT st.`name`, AVG(sc.score)
 FROM students st, scores sc
 WHERE st.id = sc.student_id
 GROUP BY st.id
 HAVING AVG(sc.score) > 60;
 #3.查询在 scores 表存在成绩的学生信息
 SELECT *
 FROM students
 WHERE students.id IN (
 	SELECT student_id
 	FROM scores
 );
 #4.查询所有同学的学生编号、学生姓名、选课总数、所有课程的总成绩(没成绩的显示为 null )
 #4.1查有成绩的学生信息
 #5.查询「李」姓老师的数量
 #6.查询学过「张三」老师授课的同学的信息
 #7.查询没有学全所有课程的同学的信息
 ```