学生、老师、课程、选课表常用sql示例

　　1、建表与准备数据

　　（1）学生表 student

DROP TABLE IF EXISTS `student`;
CREATE TABLE `student` (
  `sid` int(11) DEFAULT NULL,
  `sname` varchar(20) DEFAULT NULL,
  `sage` int(11) DEFAULT NULL,
  `ssex` varchar(20) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

-- ----------------------------
-- Records of student
-- ----------------------------
INSERT INTO `student` VALUES ('1', '刘一', '18', '男');
INSERT INTO `student` VALUES ('2', '钱二', '19', '女');
INSERT INTO `student` VALUES ('3', '张三', '17', '男');
INSERT INTO `student` VALUES ('4', '李四', '18', '女');
INSERT INTO `student` VALUES ('5', '王五', '17', '男');
INSERT INTO `student` VALUES ('6', '赵六', '19', '女');

　　（2）老师表 teacher

DROP TABLE IF EXISTS `teacher`;
CREATE TABLE `teacher` (
  `tid` int(11) DEFAULT NULL,
  `tname` varchar(20) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

-- ----------------------------
-- Records of teacher
-- ----------------------------
INSERT INTO `teacher` VALUES ('1', '叶平');
INSERT INTO `teacher` VALUES ('2', '贺高');
INSERT INTO `teacher` VALUES ('3', '杨艳');
INSERT INTO `teacher` VALUES ('4', '周磊');

　　（3）课程表 course

DROP TABLE IF EXISTS `course`;
CREATE TABLE `course` (
  `cid` int(11) DEFAULT NULL,
  `cname` varchar(255) DEFAULT NULL,
  `tid` int(11) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

-- ----------------------------
-- Records of course
-- ----------------------------
INSERT INTO `course` VALUES ('1', '语文', '1');
INSERT INTO `course` VALUES ('2', '数学', '2');
INSERT INTO `course` VALUES ('3', '英语', '3');
INSERT INTO `course` VALUES ('4', '物理', '4');

　　（4）选课表 sc

DROP TABLE IF EXISTS `sc`;
CREATE TABLE `sc` (
  `sid` int(11) DEFAULT NULL,
  `cid` int(20) DEFAULT NULL,
  `score` int(11) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

-- ----------------------------
-- Records of sc
-- ----------------------------
INSERT INTO `sc` VALUES ('1', '1', '60');
INSERT INTO `sc` VALUES ('1', '2', '78');
INSERT INTO `sc` VALUES ('1', '3', '67');
INSERT INTO `sc` VALUES ('1', '4', '58');
INSERT INTO `sc` VALUES ('2', '1', '79');
INSERT INTO `sc` VALUES ('2', '2', '81');
INSERT INTO `sc` VALUES ('2', '3', '92');
INSERT INTO `sc` VALUES ('2', '4', '68');
INSERT INTO `sc` VALUES ('3', '1', '91');
INSERT INTO `sc` VALUES ('3', '2', '47');
INSERT INTO `sc` VALUES ('3', '3', '88');
INSERT INTO `sc` VALUES ('3', '4', '56');
INSERT INTO `sc` VALUES ('4', '2', '88');
INSERT INTO `sc` VALUES ('4', '3', '90');
INSERT INTO `sc` VALUES ('4', '4', '93');
INSERT INTO `sc` VALUES ('5', '1', '46');
INSERT INTO `sc` VALUES ('5', '3', '78');
INSERT INTO `sc` VALUES ('5', '4', '53');
INSERT INTO `sc` VALUES ('6', '1', '35');
INSERT INTO `sc` VALUES ('6', '2', '68');
INSERT INTO `sc` VALUES ('6', '4', '71');

　　2、sql示例

　　（01）查询“1”课程比“2”课程成绩高的所有学生的学号；

SELECT  a.sid FROM 
(SELECT * FROM sc WHERE cid='1') a,
(SELECT * FROM sc WHERE cid='2') b
WHERE a.sid = b.sid AND a.score>b.score

SELECT a.sid FROM sc a,sc b WHERE a.sid = b.sid AND a.cid='1' AND b.cid='2' AND a.score > b.score

　　（02）查询平均成绩大于60分的同学的学号和平均成绩；

SELECT sid,AVG(score) FROM sc GROUP BY sid HAVING AVG(score) > 60

　　（03）查询所有同学的学号、姓名、选课数、总成绩；

SELECT a.sid,a.sname,b.num,b.total FROM student a,
(SELECT sid,COUNT(1) num,SUM(score) total FROM sc GROUP BY sid) b
WHERE a.sid = b.sid;

SELECT a.sid,a.sname,COUNT(sc.cid),SUM(score) FROM student a LEFT JOIN sc ON a.sid = sc.sid GROUP BY a.sid,a.sname

　　（04）查询没学过“叶平”老师课的同学的学号、姓名；

SELECT student.sid,student.sname FROM student WHERE student.sid  not in 
(SELECT sid FROM sc,course,teacher WHERE sc.cid = course.cid and course.tid = teacher.tid and teacher.tname ='叶平');

　　（05）查询学过编号“1”并且也学过编号“2”课程的同学的学号、姓名；

SELECT s.sid,s.sname FROM student s,sc a,sc b WHERE a.sid = b.sid AND a.sid = s.sid AND a.cid = '1' and b.cid = '2'

SELECT student.sid,student.sname FROM sc,student WHERE sc.sid = student.sid and sc.cid = '1' AND EXISTS
(SELECT * FROM sc sc2 WHERE sc2.sid = sc.sid and sc2.cid = '2')

　　（06）查询学过“叶平”老师所教的所有课的同学的学号、姓名；

SELECT sid,sname FROM student WHERE sid in (
SELECT sc.sid FROM teacher t,course c,sc WHERE t.tid = c.tid AND c.cid = sc.cid AND t.tname = '叶平' 
GROUP BY sc.sid HAVING COUNT(sc.cid) = (SELECT COUNT(1) FROM course c,teacher t WHERE c.tid = t.tid AND t.tname = '叶平')
)

　　（07）查询课程编号“002”的成绩比课程编号“001”课程低的所有同学的学号、姓名；

SELECT s.sid,s.sname FROM sc a,sc b,student s WHERE a.sid = b.sid AND a.sid = s.sid 
AND a.cid='2' AND b.cid = '1' AND a.score < b.score

SELECT s.sid,s.sname FROM sc,student s WHERE sc.cid = '2' AND sc.sid = s.sid AND EXISTS 
(SELECT * FROM sc sc2 WHERE sc.sid = sc2.sid AND sc2.cid = '1' AND sc.score < sc2.score)

　　（08）查询所有课程成绩小于60分的同学的学号、姓名；

SELECT * FROM student WHERE sid not in (
SELECT sc.sid FROM sc WHERE sc.score >=60
)

　　（09）查询没有学全所有课的同学的学号、姓名；

SELECT sid,sname FROM student WHERE sid in (
SELECT sc.sid FROM sc GROUP BY sc.sid HAVING COUNT(1)<(SELECT count(1) from course)
)

SELECT sc.sid,sname FROM sc,student WHERE sc.sid = student.sid GROUP BY sc.sid,sname 
HAVING COUNT(1)<(SELECT count(1) from course)

　　（10）查询至少有一门课与学号为“1001”的同学所学相同的同学的学号和姓名；

SELECT sid,sname from student WHERE sid in (
SELECT sc.sid FROM sc WHERE sc.sid !='1' AND sc.cid in (
SELECT sc.cid FROM sc WHERE sc.sid = '1'
)
)

SELECT distinct s.sid,s.sname from student s,sc WHERE s.sid = sc.sid AND s.sid != '1' 
AND sc.cid in (SELECT cid FROM sc WHERE sc.sid = '1')

　　（11）#查询和“1”号的同学学习的课程完全相同的其他同学学号和姓名；

SELECT sid,sname from student WHERE sid in (
SELECT sid from (
SELECT * from sc WHERE sc.sid != '1' AND EXISTS
(SELECT * FROM sc sc2 WHERE sc.cid = sc2.cid AND sc2.sid = '1')
) a GROUP BY sid HAVING COUNT(1)=(SELECT count(1) FROM sc WHERE sid = '1' )
)

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