MySQL 查询练习

#课程表DROP TABLE IF EXISTS `course`;CREATE TABLE `course` (  `CNO` char(5) NOT NULL,  `CNAME` varchar(10) NOT NULL,  `TNO` int(10) NOT NULL,  PRIMARY KEY (`CNO`)) ENGINE=MyISAM AUTO_INCREMENT=348 DEFAULT CHARSET=utf8;-- ------------------------------ Table structure for score-- ----------------------------#成绩表DROP TABLE IF EXISTS `score`;CREATE TABLE `score` (  `SNO` varchar(3) NOT NULL,  `CNO` varchar(5) NOT NULL,  `DEGREE` decimal(10,1) NOT NULL) ENGINE=MyISAM AUTO_INCREMENT=348 DEFAULT CHARSET=utf8;#学生表-- ------------------------------ Table structure for student-- ----------------------------DROP TABLE IF EXISTS `student`;CREATE TABLE `student` (  `SNO` int(10) NOT NULL,  `SNAME` varchar(4) NOT NULL,  `SSEX` tinyint(2) NOT NULL,  `SBIRTHDAY` datetime DEFAULT NULL,  `CLASS` varchar(5) DEFAULT NULL,  PRIMARY KEY (`SNO`)) ENGINE=MyISAM AUTO_INCREMENT=348 DEFAULT CHARSET=utf8;#教师表-- ------------------------------ Table structure for teacher-- ----------------------------DROP TABLE IF EXISTS `teacher`;CREATE TABLE `teacher` (  `TNO` varchar(3) NOT NULL,  `TNAME` varchar(4) NOT NULL,  `TSEX` tinyint(2) NOT NULL,  `TBIRTHDAY` datetime NOT NULL,  `PROF` varchar(6) DEFAULT NULL,  `DEPART` varchar(10) NOT NULL,  PRIMARY KEY (`TNO`)) ENGINE=MyISAM AUTO_INCREMENT=348 DEFAULT CHARSET=utf8;

 以课程号升序、成绩降序查询成绩表的所有记录。 SELECT * from score ORDER BY cno asc, degree DESC;

 查询“95031”班的学生人数。SELECT COUNT(CLASS) as 9501班 FROM student WHERE class="95033";

查询‘3-105’号课程的平均分SELECT AVG(degree) FROM score WHERE CNO="3-105";SELECT avg(degree) 平均分  from score GROUP BY cno HAVING cno = ‘3-105‘;

查询成绩表中至少有5名学生选修的并以3开头的课程的平均分数。SELECT CNO,avg(degree) from score  GROUP BY CNO HAVING  COUNT(*)>5 and CNO like "3%";查询最低分大于70，最高分小于90的学生编号 列SELECT SNO  from score  GROUP BY SNO HAVING  min(DEGREE)>70 and MAX(DEGREE)<90;

查询选修“3-105”课程的成绩高于“109”号同学成绩的所有同学的记录。SELECT  stu.* from  student stu LEFT JOIN score sc ON sc.SNO=stu.SNO and cno="3-105" and sc.DEGREE>(SELECT degree FROM score WHERE CNO="3-105" AND SNO=109 )

查询score中选学一门以上课程的同学中分数为非最高分成绩的记录。SELECT score.* from score INNER JOIN (SELECT sno ,MAX(degree) as maxdegree from score GROUP BY sno HAVING COUNT(*) >1) temp on score.sno = temp.sno and score.degree < temp.maxdegree;查询和学号为107的同学同年出生的所有学生的Sno、Sname和Sbirthday列SELECT sno,sname,sbirthday FROM student WHERE YEAR(SBIRTHDAY)=(SELECT YEAR(SBIRTHDAY) from student WHERE SNO=107);查询“张旭“教师任课的学生成绩SELECT * from score WHERE cno in (SELECT cno from course WHERE tno = (SELECT tno from teacher WHERE tname =‘张旭‘));

查询出“计算机系“教师所教课程的成绩表。
SELECT * from score WHERE cno in (SELECT CNO from course WHERE TNO in (SELECT tno from teacher WHERE DEPART = ‘计算机系‘));

查询“计算机系”与“电子工程系“不同职称的教师的名字和职称。
SELECT tname ,prof from teacher WHERE DEPART = ‘计算机系‘ and  prof not in (SELECT prof from teacher WHERE DEPART = ‘电子工程系‘)
UNION
SELECT tname ,prof from teacher WHERE DEPART = ‘电子工程系‘ and  prof not in (SELECT prof from teacher WHERE DEPART = ‘计算机系‘);

查询所有教师和同学的名字、性别和生日.
SELECT sname as name , ssex as sex , sbirthday as birthday from student
UNION ALL #万一老师和学生姓名 性别 出生日相同呢 所以加了ALL
SELECT tname , tsex  , tbirthday as birthday from teacher;