293 lines
10 KiB
SQL
293 lines
10 KiB
SQL
USE hutao;
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CREATE TABLE IF NOT EXISTS
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student_info
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(
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number INT PRIMARY KEY COMMENT '学生ID信息表的主键',
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name VARCHAR(5) NOT NULL COMMENT '学生姓名',
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sex ENUM('男', '女') COMMENT '学生性别',
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id_number CHAR(18) COMMENT '身份证',
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department VARCHAR(30) COMMENT '学院',
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major VARCHAR(30) COMMENT '专业',
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enrollment_time DATE COMMENT '入学时间',
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UNIQUE KEY id_number (id_number)
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) COMMENT '学生信息表';
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CREATE TABLE IF NOT EXISTS
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student_score
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(
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number INT COMMENT '学生ID',
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subject VARCHAR(30) COMMENT '学科',
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score INT NOT NULL COMMENT '成绩',
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PRIMARY KEY (number, subject),
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CONSTRAINT FOREIGN KEY (number) REFERENCES student_info(number)
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) COMMENT '学生成绩表';
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SHOW CREATE TABLE student_info;
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INSERT INTO
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student_info(number, name, sex, id_number, department, major, enrollment_time)
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VALUES
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(20210101, '狗哥', '男', '158177200301044792', '计算机学院', '计算机科学与工程', '2021-09-01'),
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(20210102, '猫爷', '男', '151008200201178529', '计算机学院', '计算机科学与工程', '2021-09-01'),
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(20210103, '艾希', '女', '17156320010116959X', '计算机学院', '软件工程', '2021-09-01'),
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(20210104, '亚索', '男', '141992200201078600', '计算机学院', '计算机科学与工程', '2021-09-01'),
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(20210105, '莫甘娜', '女', '181048200008156368', '航天学院', '飞行器设计', '2021-09-01'),
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(20210106, '赵信', '男', '197995200201078445', '航天学院', '电子信息', '2021-09-01');
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INSERT INTO
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student_score(number, subject, score)
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VALUES
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(20210101, '计算机是怎样运行的', 78),
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(20210101, 'MySQL是怎样运行的', 88),
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(20210102, '计算机是怎样运行的', 100),
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(20210102, 'MySQL是怎样运行的', 98),
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(20210103, '计算机是怎样运行的', 59),
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(20210103, 'MySQL是怎样运行的', 61),
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(20210104, '计算机是怎样运行的', 55),
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(20210104, 'MySQL是怎样运行的', 46);
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USE hutao;
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SELECT * FROm student_info;
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SELECT * FROM student_score;
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# 查询单列
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SELECT student_info.number FROM student_info;
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# 列的别名
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SELECT number '学号' FROM student_info;
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# 查询多列
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SELECT number, name, id_number, major FROM student_info;
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SELECT number '学号', name '姓名', id_number '身份证号', major '专业' FROM student_info;
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# 查询去重
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SELECT DISTINCT department FROM student_info;
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SELECT DISTINCT department, major FROM student_info;
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# 分页
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# 查询前两条
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SELECT * FROM student_info LIMIT 2;
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# 查询两条，从5+1开始
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SELECT * FROM student_info LIMIT 5, 2;
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# 排序
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SELECT student_info.number FROM student_info ORDER BY student_info.number ASC;
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SELECT * FROM student_info ORDER BY student_info.number ASC;
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SELECT * FROM student_info ORDER BY student_info.number DESC;
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# 多列排序
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SELECT * FROM student_score ORDER BY subject, score DESC;
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# 简单查询
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# 查id等于20210101的学生的所有成绩
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SELECT * FROM student_score WHERE number = 20210101;
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# 查看除了这个学生的其他的学生的成绩
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SELECT * FROM student_score WHERE number != 20210101;
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SELECT * FROM student_score WHERE number <> 20210101;
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-- 查成绩及格
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SELECT * FROM student_score WHERE score >= 60;
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# 查成绩不及格
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SELECT * FROM student_score WHERE score < 60;
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# 查成绩在60到80之间的成绩
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SELECT * FROM student_score WHERE score BETWEEN 60 AND 80;
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# 查成绩不在60到80之间的成绩
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SELECT * FROM student_score WHERE score NOT BETWEEN 60 AND 80;
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-- 匹配查询
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SELECT * FROM student_info WHERE major IN ('软件工程', '飞行器设计');
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SELECT * FROM student_info WHERE major NOT IN ('软件工程', '飞行器设计');
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-- NULL
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SELECT * FROM student_info WHERE name IS NULL;
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SELECT * FROM student_info WHERE name IS NOT NULL;
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-- 多条件查询
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-- AND
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SELECT * FROM student_info WHERE sex = '男' AND department = '计算机学院';
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-- OR
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SELECT * FROM student_info WHERE sex = '男' OR department = '计算机学院';
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-- 复杂条件搜索
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-- sorce < 60 + subject = 'MySQL是怎样运行的'
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-- source > 90
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SELECT * FROM student_score WHERE score > 90 OR score < 60 AND student_score.subject = 'MySQL是怎样运行的';
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-- source > 90 + sorce < 60
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-- subject = 'MySQL是怎样运行的'
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SELECT * FROM student_score WHERE (score > 90 OR score < 60) AND student_score.subject = 'MySQL是怎样运行的';
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-- 通配符
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SELECT * FROM student_info WHERE name LIKE '狗%';
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SELECT * FROM student_info WHERE name LIKE '%甘%';
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SELECT * FROM student_info WHERE name LIKE '狗__';
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-- 转义通配符
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SELECT * FROM student_info WHERE name LIKE '狗\__';
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SELECT * FROM student_info WHERE name LIKE '狗\%_';
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-- 表达式
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-- 放在SELECT中
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SELECT number, subject, score + 100 FROM student_score;
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SELECT number, subject, score + 100 AS `score` FROM student_score;
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-- ``用来装列名,''用来装普通字符串
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SELECT name, '我是一个装饰', `sex`, 'sex' FROM student_info;
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-- 不能用``将不是列明的内容装起来
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SELECT name, `我是一个装饰` FROM student_info;
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-- 计算器
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SELECT 5 * 6 +128 -32;
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-- 放在WHERE中
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-- 假 查不出来数据
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SELECT * FROM student_info WHERE 0;
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SELECT * FROM student_info WHERE NULL;
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SELECT * FROM student_info WHERE 2 - 2;
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SELECT * FROM student_info WHERE 2 < 1;
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-- 真 查出所有数据
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SELECT * FROM student_info WHERE 2 > 1;
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SELECT * FROM student_info WHERE 2 + 2;
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SELECT * FROM student_info WHERE 2;
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-- 表达式中的NULL
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SELECT 1>NULL, 2-NULL;
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SELECT NULL IS NULL;
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-- 字符处理函数
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-- LEFT
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SELECT LEFT('abc123', 4); -- abc1
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-- RIGHT
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SELECT RIGHT('abc123',2); -- 23
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-- LENGTH
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SELECT LENGTH('何先生'); -- 9
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-- LOWER
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SELECT LOWER('ABCDEF'); -- abcdef
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-- UPPER
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SELECT UPPER('abcdef'); -- ABCDEF
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-- LTRIM
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SELECT LTRIM(' ABC'); -- 'ABC'
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SELECT ' ABC'; -- ' ABC'
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-- RTRIM
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SELECT RTRIM(' ABC '); -- ' ABC'
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-- TRIM
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SELECT TRIM(' A B C '); -- 'A B C'
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-- SUBSTRING
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SELECT SUBSTRING('何先生abcdefg何先生', 2, 5); -- '先生abc'
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-- CONCAT
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SELECT CONCAT('a_', 'b', 'CD21', 'AA'); -- 'a_bCD21AA'
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-- CHAR_LENGTH
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SELECT CHAR_LENGTH('何先生abcdefg何先生'); -- 13
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-- 和数据库结合使用
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SELECT CONCAT('学号为', number, '的同学在《', subject, '》课程上的成绩是：', score) AS '成绩描述' FROM student_score;
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-- 时间格式化
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SELECT DATE_FORMAT(NOW(), '%Y年%m月%d日 %H:%i|%s 星期%w');
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-- 2024年03月30日 06:07|31 星期6
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-- 流程控制
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SELECT
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*,
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CASE
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WHEN score < 60 THEN '不及格'
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WHEN score < 90 THEN '及格'
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ELSE '优秀'
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END AS '评价'
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FROM
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student_score;
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SELECT
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name, department, major,
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CASE department
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WHEN '计算机学院' THEN '一级学院'
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WHEN '航天学院' THEN '二级学院'
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ELSE '未设定'
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END AS '学院类别'
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FROM
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student_info;
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# 聚合函数、汇总函数
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SELECT COUNT(number) AS '人数', MAX(student_score.score) AS '最高分', MIN(student_score.score) AS '最低分', AVG(student_score.score) AS '平均分', SUM(student_score.score) AS '总分' FROM student_score;
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-- 分组查询
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SELECT subject, COUNT(subject) AS '考试人数' FROM student_score GROUP BY subject;
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-- 带有WHERE子句的分组查询
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SELECT subject, COUNT(subject) AS '及格人数' FROM student_score WHERE score > 60 GROUP BY subject;
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-- 作用于分组的过滤条件
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SELECT subject, AVG(score) FROM student_score WHERE score > 60 GROUP BY subject HAVING MAX(score) > 90 AND AVG(score) > 80;
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SELECT subject, AVG(score) FROM student_score GROUP BY subject HAVING MAX(score) > 90 AND AVG(score) > 70 AND subject != 'MySQL是怎样运行的';
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SELECT subject, AVG(score) FROM student_score WHERE subject != 'MySQL是怎样运行的' GROUP BY subject HAVING MAX(score) > 90 AND AVG(score) > 70;
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-- 分组排序
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SELECT student_score.subject, AVG(student_score.score) FROM student_score GROUP BY student_score.subject ORDER BY AVG(score) DESC;
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-- 多个分组列
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SELECT department, major, COUNT(number) AS '人数' FROM student_info GROUP BY department, major;
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-- 分组采用表达式
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SELECT student_score.subject, COUNT(student_score.number) AS 人数 FROM student_score GROUP BY CONCAT('学科:', subject)
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-- 普通连接 和内连接是等价的
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SELECT * FROM student_info a, student_score b WHERE a.number = b.number;
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-- 左外连接，以a表为基准查出所有
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SELECT * FROM student_info a LEFT OUTER JOIN student_score b ON a.number = b.number;
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-- 右外连接
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SELECT * FROM student_info a RIGHT OUTER JOIN student_score b ON a.number = b.number;
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-- 自连接，查看和狗哥专业相同的人员信息
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SELECT * FROm student_info a JOIN student_info b ON a.major = b.major WHERE a.name = '狗哥';
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-- 单表组合查询
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SELECT name, student_info.department, student_info.major FROM student_info WHERE sex = '男' OR number > 20210101;
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SELECT name, student_info.department, student_info.major FROM student_info WHERE sex = '男' UNION SELECT student_info.department, name, student_info.major FROM student_info WHERE number > 20210101;
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-- 14章插入建表
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CREATE table first_table(
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first_column INT,
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second_column VARCHAR(100)
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);
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-- 插入数据
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-- 不写列明 默认按照建表的顺序 （每列必须明确写出值，可以用NULL替代）
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INSERT INTO first_table VALUE (1, '哈哈');
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-- 指定列名
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INSERT INTO first_table(first_column, second_column) VALUE (2, '嘿嘿');
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-- 可以调换列顺序
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INSERT INTO first_table(second_column, first_column) VALUE ('嘿嘿嘿', 3);
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-- 批量插入数据 VALUE => VALUES （VALUES也可以只插入一条数据）
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INSERT INTO
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first_table(second_column, first_column)
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VALUE
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('嘿哈', 5),
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('嗯哼', 6),
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('唉嘿', 7),
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('嘻嘻', 8),
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('呜呜呜', 9);
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-- 插入其他表的数据
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INSERT INTO first_table SELECT * FROM first_table LIMIT 4;
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INSERT INTO first_table(first_column, second_column) SELECT first_column, second_column FROM first_table WHERE first_column = 3;
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-- 删除记录
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DELETE FROM first_table;
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-- 创建存储函数
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-- 设置分隔符
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SET global log_bin_trust_function_creators = TRUE;
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DELIMITER $
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CREATE FUNCTION get_score_avg(subject_name VARCHAR(10))
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RETURNS DOUBLE
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BEGIN
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RETURN (SELECT AVG(student_score.score) FROM student_score WHERE subject = subject_name);
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END $
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DELIMITER ;
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SHOW FUNCTION STATUS ;
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