数据表
/* Navicat SQLite Data Transfer Source Server : school Source Server Version : 30808 Source Host : :0 Target Server Type : SQLite Target Server Version : 30808 File Encoding : 65001 Date: 2021-12-23 16:06:04 */ PRAGMA foreign_keys = OFF; -- ---------------------------- -- Table structure for Course -- ---------------------------- DROP TABLE IF EXISTS "main"."Course"; CREATE TABLE Course( courseid integer primary key autoincrement, courseme varchar(32), teacherid int ); -- ---------------------------- -- Records of Course -- ---------------------------- INSERT INTO "main"."Course" VALUES (3001, '语文', 1001); INSERT INTO "main"."Course" VALUES (3002, '数学', 1002); -- ---------------------------- -- Table structure for Mark -- ---------------------------- DROP TABLE IF EXISTS "main"."Mark"; CREATE TABLE Mark( userid integer, courseid integer not null, score int default 0 ); -- ---------------------------- -- Records of Mark -- ---------------------------- INSERT INTO "main"."Mark" VALUES (2001, 3001, 89); INSERT INTO "main"."Mark" VALUES (2001, 3002, 90); INSERT INTO "main"."Mark" VALUES (2002, 3001, 66); INSERT INTO "main"."Mark" VALUES (2003, 3002, 85); -- ---------------------------- -- Table structure for sqlite_sequence -- ---------------------------- DROP TABLE IF EXISTS "main"."sqlite_sequence"; CREATE TABLE sqlite_sequence(name,seq); -- ---------------------------- -- Records of sqlite_sequence -- ---------------------------- INSERT INTO "main"."sqlite_sequence" VALUES ('Teacher', 1002); INSERT INTO "main"."sqlite_sequence" VALUES ('Student', 2002); INSERT INTO "main"."sqlite_sequence" VALUES ('Course', 3002); -- ---------------------------- -- Table structure for Student -- ---------------------------- DROP TABLE IF EXISTS "main"."Student"; CREATE TABLE Student( userid integer primary key autoincrement, username varchar(32), userage int, usersex varchar(32) ); -- ---------------------------- -- Records of Student -- ---------------------------- INSERT INTO "main"."Student" VALUES (2001, '小明', 18, '男'); INSERT INTO "main"."Student" VALUES (2002, '小红', 18, '女'); -- ---------------------------- -- Table structure for Teacher -- ---------------------------- DROP TABLE IF EXISTS "main"."Teacher"; CREATE TABLE Teacher( teacherid integer primary key autoincrement, teachername varchar(32) ); -- ---------------------------- -- Records of Teacher -- ---------------------------- INSERT INTO "main"."Teacher" VALUES (1001, '张三'); INSERT INTO "main"."Teacher" VALUES (1002, '李四');
问题:
1、查询“语文”课程比“数学”课程成绩低的所有学生的学号
select a.userid from (select userid,score from Mark where courseid ='3001')a, (select userid,score from Mark where courseid ='3002')b where a.userid = b.userid and a.score
2、查询平均成绩大于60分的同学的学号和平均成绩
select userid,avg(score) from Mark group by userid having avg(score)>60;
3、查询所有同学的学号、姓名、选课数、总成绩
select s.userid ,s.username ,count_courseid as 选课数, sum_score as 总成绩 from Student s left join (select userid,count(courseid ) as count_courseid,sum(score) as sum_score from Mark group by userid )sc on s.userid = sc.userid;
4、查询姓‘李'的老师的个数:
select count(teachername ) from Teacher where teachername like '张%';
5、检索语文课程分数小于60,按分数降序排列的同学学号:
select userid ,score from Mark where courseid ='3001' and score<60 order by score desc;
6、查询学/没学过”张三”老师讲授的任一门课程的学生姓名
select username from Student where userid in ( select userid from Mark,Course,Teacher where Course.teacherid = Teacher.teacherid and Mark.courseid = Course.courseid and Teacher.teachername ='张三' );
7、查询全部学生选修的课程和课程号和课程名:
select courseid ,courseme from Course where courseid in (select courseid from Mark group by courseid);
8、检索选修两门课程的学生学号:
select userid from Mark group by userid having count(8) == 2;
9、查询各个课程及相应的选修人数
select courseid ,count(*) from Course group by courseid ;
10、查询选修“张三”老师所授课程的学生中,成绩最高的学生姓名及其成绩
select Student.username ,Mark.score from Mark left join Student on Mark.userid = Student.userid left join Course on Mark.courseid = Course.courseid left join Teacher on Course.teacherid = Teacher.teacherid where Teacher.teachername = '张三' and Mark.score = ( select max(score) from Mark sc_1 where Mark.courseid = sc_1.courseid);
11、求选了课程的学生人数:
select count(2) from (select distinct userid from Mark)a;
12、查询课程编号为“语文”且课程成绩在80分以上的学生的学号和姓名
select Mark.userid,Student.username from Mark left join Student on Mark.userid = Student.userid where Mark.courseid = '3001' and Mark.score>80;
13、查询每门课程的平均成绩,结果按平均成绩升序排序,平均成绩相同时,按课程号降序排列
select courseid ,avg(score) from Mark group by courseid order by avg(score),courseid desc;
14、查询课程名称为“数学”,且分数高于85的学生名字和分数:
select c.courseme ,Student.userid ,Student.username ,Mark.score from Course c left join Mark on Mark.courseid = c.courseid LEFT JOIN Student on Student.userid = Mark.userid where c.courseme = '数学' and Mark.score>85;
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