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2207/MySQL练习题/查询练习.md

@@ -177,4 +177,93 @@ 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
+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
+```
+