MySQL常用函数，和聚合函数简单应用
2024-07-03 04:31:30
#SQL脚本
/*
SQLyog 企业版 - MySQL GUI v8.14
MySQL - 5.5.40 : Database - school
*********************************************************************
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/*Table structure for table `category` */DROP TABLE IF EXISTS `category`;CREATE TABLE `category` (`categoryid` int(10) unsigned NOT NULL AUTO_INCREMENT,`pid` int(10) NOT NULL,`categoryName` varchar(50) NOT NULL,PRIMARY KEY (`categoryid`)
) ENGINE=InnoDB AUTO_INCREMENT=9 DEFAULT CHARSET=utf8;/*Data for the table `category` */insert into `category`(`categoryid`,`pid`,`categoryName`) values (2,1,'美术设计'),(3,1,'软件开发'),(4,3,'数据库基础'),(5,2,'ps基础'),(6,2,'色彩搭配'),(7,3,'PHP基础'),(8,3,'Java基础');/*Table structure for table `grade` */DROP TABLE IF EXISTS `grade`;CREATE TABLE `grade` (`GradeID` int(11) NOT NULL AUTO_INCREMENT COMMENT '年级编号',`GradeName` varchar(50) NOT NULL COMMENT '年级名称',PRIMARY KEY (`GradeID`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8;/*Data for the table `grade` */insert into `grade`(`GradeID`,`GradeName`) values (1,'大一'),(2,'大二'),(3,'大三'),(4,'大四'),(5,'预科班');/*Table structure for table `result` */DROP TABLE IF EXISTS `result`;CREATE TABLE `result` (`StudentNo` int(4) NOT NULL COMMENT '学号',`SubjectNo` int(4) NOT NULL COMMENT '课程编号',`ExamDate` datetime NOT NULL COMMENT '考试日期',`StudentResult` int(4) NOT NULL COMMENT '考试成绩',KEY `SubjectNo` (`SubjectNo`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;/*Data for the table `result` */insert into `result`(`StudentNo`,`SubjectNo`,`ExamDate`,`StudentResult`) values (1000,1,'2013-11-11 16:00:00',94),(1000,2,'2012-11-10 10:00:00',75),(1000,3,'2011-12-19 10:00:00',76),(1000,4,'2010-11-18 11:00:00',93),(1000,5,'2013-11-11 14:00:00',97),(1000,6,'2012-09-13 15:00:00',87),(1000,7,'2011-10-16 16:00:00',79),(1000,8,'2010-11-11 16:00:00',74),(1000,9,'2013-11-21 10:00:00',69),(1000,10,'2012-11-11 12:00:00',78),(1000,11,'2011-11-11 14:00:00',66),(1000,12,'2010-11-11 15:00:00',82),(1000,13,'2013-11-11 14:00:00',94),(1000,14,'2012-11-11 15:00:00',98),(1000,15,'2011-12-11 10:00:00',70),(1000,16,'2010-09-11 10:00:00',74),(1001,1,'2013-11-11 16:00:00',76),(1001,2,'2012-11-10 10:00:00',93),(1001,3,'2011-12-19 10:00:00',65),(1001,4,'2010-11-18 11:00:00',71),(1001,5,'2013-11-11 14:00:00',98),(1001,6,'2012-09-13 15:00:00',74),(1001,7,'2011-10-16 16:00:00',85),(1001,8,'2010-11-11 16:00:00',69),(1001,9,'2013-11-21 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16:00:00',97),(1003,8,'2010-11-11 16:00:00',77),(1003,9,'2013-11-21 10:00:00',62),(1003,10,'2012-11-11 12:00:00',81),(1003,11,'2011-11-11 14:00:00',76),(1003,12,'2010-11-11 15:00:00',61),(1003,13,'2013-11-11 14:00:00',93),(1003,14,'2012-11-11 15:00:00',79),(1003,15,'2011-12-11 10:00:00',78),(1003,16,'2010-09-11 10:00:00',96),(1004,1,'2013-11-11 16:00:00',84),(1004,2,'2012-11-10 10:00:00',79),(1004,3,'2011-12-19 10:00:00',76),(1004,4,'2010-11-18 11:00:00',78),(1004,5,'2013-11-11 14:00:00',81),(1004,6,'2012-09-13 15:00:00',90),(1004,7,'2011-10-16 16:00:00',63),(1004,8,'2010-11-11 16:00:00',89),(1004,9,'2013-11-21 10:00:00',67),(1004,10,'2012-11-11 12:00:00',100),(1004,11,'2011-11-11 14:00:00',94),(1004,12,'2010-11-11 15:00:00',65),(1004,13,'2013-11-11 14:00:00',86),(1004,14,'2012-11-11 15:00:00',77),(1004,15,'2011-12-11 10:00:00',82),(1004,16,'2010-09-11 10:00:00',87),(1005,1,'2013-11-11 16:00:00',82),(1005,2,'2012-11-10 10:00:00',92),(1005,3,'2011-12-19 10:00:00',80),(1005,4,'2010-11-18 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10:00:00',99),(1017,16,'2010-09-11 10:00:00',76);/*Table structure for table `student` */DROP TABLE IF EXISTS `student`;CREATE TABLE `student` (`StudentNo` int(4) NOT NULL COMMENT '学号',`LoginPwd` varchar(20) DEFAULT NULL,`StudentName` varchar(20) DEFAULT NULL COMMENT '学生姓名',`Sex` tinyint(1) DEFAULT NULL COMMENT '性别，取值0或1',`GradeId` int(11) DEFAULT NULL COMMENT '年级编号',`Phone` varchar(50) NOT NULL COMMENT '联系电话，允许为空，即可选输入',`Address` varchar(255) NOT NULL COMMENT '地址，允许为空，即可选输入',`BornDate` datetime DEFAULT NULL COMMENT '出生时间',`Email` varchar(50) NOT NULL COMMENT '邮箱账号，允许为空，即可选输入',`IdentityCard` varchar(18) DEFAULT NULL COMMENT '身份证号',PRIMARY KEY (`StudentNo`),UNIQUE KEY `IdentityCard` (`IdentityCard`),KEY `Email` (`Email`),FULLTEXT KEY `StudentName` (`StudentName`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;/*Data for the table `student` */insert into `student`(`StudentNo`,`LoginPwd`,`StudentName`,`Sex`,`GradeId`,`Phone`,`Address`,`BornDate`,`Email`,`IdentityCard`) values (1000,'111111','郭靖',1,1,'13500000001','北京海淀区中关村大街1号','1986-12-11 00:00:00','test1@bdqn.cn','450323198612111234'),(1001,'123456','李文才',1,2,'13500000002','河南洛阳','1981-12-31 00:00:00','test1@bdqn.cn','450323198112311234'),(1002,'111111','李斯文',1,1,'13500000003','天津市和平区','1986-11-30 00:00:00','test1@bdqn.cn','450323198611301234'),(1003,'123456','武松',1,3,'13500000004','上海卢湾区','1986-12-31 00:00:00','test1@bdqn.cn','450323198612314234'),(1004,'123456','张三',1,4,'13500000005','北京市通州','1989-12-31 00:00:00','test1@bdqn.cn','450323198612311244'),(1005,'123456','张秋丽 ',2,1,'13500000006','广西桂林市灵川','1986-12-31 00:00:00','test1@bdqn.cn','450323198612311214'),(1006,'123456','肖梅',2,4,'13500000007','地址不详','1986-12-31 00:00:00','test1@bdqn.cn','450323198612311134'),(1007,'111111','欧阳峻峰',1,1,'13500000008','北京东城区','1986-12-31 00:00:00','test1@bdqn.cn','450323198612311133'),(1008,'111111','梅超风',1,1,'13500000009','河南洛阳','1986-12-31 00:00:00','test1@bdqn.cn','450323198612311221'),(1009,'123456','刘毅',1,2,'13500000011','安徽','1986-12-31 00:00:00','test1@bdqn.cn','450323198612311231'),(1010,'111111','大凡',1,1,'13500000012','河南洛阳','1986-12-31 00:00:00','test1@bdqn.cn','450323198612311044'),(1011,'111111','奥丹斯',1,1,'13500000013','北京海淀区中关村大街*号','1984-12-31 00:00:00','test1@bdqn.cn','450323198412311234'),(1012,'123456','多伦',2,3,'13500000014','广西南宁中央大街','1986-12-31 00:00:00','test1@bdqn.cn','450323198612311334'),(1013,'123456','李梅',2,1,'13500000015','上海卢湾区','1986-12-31 00:00:00','test1@bdqn.cn','450323198612311534'),(1014,'123456','张得',2,4,'13500000016','北京海淀区中关村大街*号','1986-12-31 00:00:00','test1@bdqn.cn','450323198612311264'),(1015,'123456','李东方',1,4,'13500000017','广西桂林市灵川','1976-12-31 00:00:00','test1@bdqn.cn','450323197612311234'),(1016,'111111','刘奋斗',1,1,'13500000018','上海卢湾区','1986-12-31 00:00:00','test1@bdqn.cn','450323198612311251'),(1017,'123456','可可',2,3,'13500000019','北京长安街1号','1981-09-10 00:00:00','test1@bdqn.cn','450323198109108311'),(10066,'','Tom',1,1,'13500000000','','0000-00-00 00:00:00','email@22.com','33123123123123123'),(8888,'111111','小红',1,1,'13500000888','北京海淀区中关村大街1号',NULL,'test1@163.cn','450323198612111889'),(8889,'123456','小%',1,2,'13500000666','河南洛阳',NULL,'test1@126.cn','450323198112311999'),(2000,'123456','无名',NULL,NULL,'13500000777','上海',NULL,'unname@bdqn.cn','421123199307275618');/*Table structure for table `subject` */DROP TABLE IF EXISTS `subject`;CREATE TABLE `subject` (`SubjectNo` int(11) NOT NULL AUTO_INCREMENT COMMENT '课程编号',`SubjectName` varchar(50) DEFAULT NULL COMMENT '课程名称',`ClassHour` int(4) DEFAULT NULL COMMENT '学时',`GradeID` int(4) DEFAULT NULL COMMENT '年级编号',PRIMARY KEY (`SubjectNo`)
) ENGINE=InnoDB AUTO_INCREMENT=18 DEFAULT CHARSET=utf8;/*Data for the table `subject` */insert into `subject`(`SubjectNo`,`SubjectName`,`ClassHour`,`GradeID`) values (1,'高等数学-1',110,1),(2,'高等数学-2',110,2),(3,'高等数学-3',100,3),(4,'高等数学-4',130,4),(5,'C语言-1',110,1),(6,'C语言-2',110,2),(7,'C语言-3',100,3),(8,'C语言-4',130,4),(9,'JAVA第一学年',110,1),(10,'JAVA第二学年',110,2),(11,'JAVA第三学年',100,3),(12,'JAVA第四学年',130,4),(13,'数据库结构-1',110,1),(14,'数据库结构-2',110,2),(15,'数据库结构-3',100,3),(16,'数据库结构-4',130,4),(17,'C#基础',130,1);/*Table structure for table `test3` */DROP TABLE IF EXISTS `test3`;CREATE TABLE `test3` (`id` int(4) NOT NULL DEFAULT '0',`testno` varchar(10) DEFAULT NULL,`c` varchar(50) DEFAULT NULL,`d` varchar(50) DEFAULT NULL,`e` text,FULLTEXT KEY `e` (`e`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;/*Data for the table `test3` *//*!40101 SET SQL_MODE=@OLD_SQL_MODE */;
/*!40014 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS */;
/*!40014 SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS */;
/*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;
#数学函数
SELECT ABS(-8);#绝对值
SELECT CEILING(9.8);#大于等于我的最小的整数
SELECT FLOOR(9.3) ;#大于等于我的最大的整数
SELECT RAND();#返回0到1之间的随机数
SELECT RAND(10);#以某个数作为种子生成固定随机数
SELECT SIGN(-9);#0返回0，正数返回1，负数返回-1
#字符串函数
SELECT CHAR_LENGTH('好好学习数据库');#返回字符串长度
SELECT CONCAT('一','二','三');#合并字符串，参数可以有一个可以有多个CONCAT('%',李,'%');
SELECT INSERT('一三五七九',1,5,'二四六八十');#替换字符串，从某个(下标从1开始)位置开始,替换某个长度的字符串，替换的值可以与被替换的值不同
SELECT LOWER('GIVE ME');#变小写
SELECT UPPER('give me');#变大写
SELECT LEFT('一二三四五',3);#从左边截取字符串
SELECT RIGHT('一二三四五',3);#从右边边截取字符串
SELECT REPLACE('你好','你','你们');#替换
SELECT SUBSTR('中国欢迎你',1,2);#截取字符串
SELECT REVERSE('五四三二一');#反转字符串
#日期和时间函数
SELECT CURRENT_DATE();#获取当前日期
SELECT CURDATE();#获取当前日期
SELECT NOW();#获取当前的日期和时间
SELECT LOCALTIME();#获取当前的日期和时间
SELECT SYSDATE();#获取当前的日期和时间
#分别获取日期中的某个部分
SELECT YEAR(NOW());#年
SELECT MONTH(NOW());#月
SELECT DAY(NOW());#日
SELECT HOUR(NOW());#时
SELECT MINUTE(NOW());#分
SELECT SECOND(NOW());#秒
#系统信息函数
SELECT VERSION();#查询数据库版本
SELECT USER();#查询当前用户#查询姓李的同学，将李改成历
SELECT REPLACE(studentname,'李','历') AS 新名字 FROM student
WHERE studentname LIKE CONCAT('李','%');#聚合函数-统计函数
#COUNT();SUM();AVG();MAX();MIN();graderesult
SELECT COUNT(studentname) FROM student;
SELECT COUNT(*) FROM student;
SELECT COUNT(1) FROM student;SELECT SUM(studentresult) AS 总和 FROM result;
SELECT AVG(studentresult) AS 平均分 FROM result;
SELECT MAX(studentresult) AS 最高分 FROM result;
SELECT MIN(studentresult) AS 最低分 FROM result;SELECT COUNT(studentno='1000') FROM result;SELECT SUM(studentno) FROM result GROUP BY studentno;#统计每个学生参加了多少次考试
SELECT s.StudentNo,s.StudentName, SUM(r.studentno IN(
s.studentno
)) FROM result r,student s
WHERE r.StudentNo=s.StudentNo
GROUP BY r.StudentNo;
#查询不同课程的平均分，最高分，最低分#分完组以后再去设定条件，等同于where
SELECT r.subjectno,sub.subjectname, SUM(studentresult) AS 总分, AVG(studentresult) AS 平均分,MAX(studentresult) AS 最高分,MIN(studentresult) AS 最低分
FROM result r,`subject` sub
WHERE r.SubjectNo=sub.SubjectNo
GROUP BY subjectno
HAVING 平均分>80
ORDER BY 平均分 DESC
LIMIT 0,4;
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