MySQL

环境说明

mysql5.14社区版免费

navicat15

安装视频教程：https://www.bilibili.com/video/BV1H44y1W7F9?spm_id_from=333.337.search-card.all.click&vd_source=a25fe0c73eb730c360192de341c08931

链接：https://pan.baidu.com/s/1sKIpLTt2Sy-qAmOTdOqncw
提取码：kksk

创建数据库

# 演示数据库操作
# 创建一个whm_db01数据库 默认校对规则是utf8_generate_ci
CREATE DATABASE whm_db01;# 删除数据库指令
DROP DATABASE whm_db01;# 创建一个使用utf8字符集的whm_db02数据库
CREATE DATABASE whm_db02 CHARACTER SET utf8;# 创建一个使用utf8字符集，并带校验规则的whm_db03数据库
CREATE DATABASE whm_db03 CHARACTER SET utf8 COLLATE utf8_bin;# 查表中元素 utf8_bin区分大小写， 默认校对规则是utf8_generate_ci不区分
SELECT * FROM t1 WHERE NAME = 'TOM'

查询数据库

# 显示数据库语句
SHOW DATABASES;# 显示创建数据库创建语句
SHOW CREATE DATABASE `whm_db01`;
# 在创建数据库，表的时候，为了规避关键字，可以使用反引号解决 ` `
# 数据库删除语句
DROP DATABASE `whm_db01`

备份和恢复数据库

备份数据库（注意在DOS执行）命令行

mysqldump -u 用户名 -p -B 数据库1 数据库2 数据库n > 文件名.sql

恢复数据库（注意进入Mysql命令行再执行）

Source 文件名.sql

第二种恢复方法，直接讲bak.sql直接粘贴到查询编辑器中执行

mysqldump -u 用户名 -p 数据库1 表1…表n > 文件名.sql

创建表

CREATE TABLE table_name(

field1 datatype,

field2 datatype,

field3 datatype

)character set字符集 collate校对规则 engine存储引擎

field指定列名 datatype指定列类型

如果varchar不够用，可以使用text 还不够使用mediumtext 还不够使用longtext

修改表

增删修改表的列：

ALTER TABLE tablename

ADD (column datatype);

MODIFY (column datatype);

DROP (column);

# 修改表的操作练习
DESC employee; # 显示表结构
ALTER TABLE `emp` ADD image VARCHAR(32) NOT NULL DEFAULT '' AFTER RESUME;ALTER TABLE `emp` MODIFY job VARCHAR(60) NOT NULL DEFAULT '';ALTER TABLE `emp` DROP sex;RENAME TABLE `emp` TO employee;ALTER TABLE employee CHARACTER set utf8;ALTER TABLE employee CHANGE NAME user_name VARCHAR(32) NOT NULL DEFAULT '';

insert语句

# 练习insert语句
CREATE TABLE `goods`(id INT,goods_name VARCHAR(10),price DOUBLE
);INSERT INTO `goods` (id, goods_name, price)VALUE(10, 'huawei', 2000);INSERT INTO `goods` (id, goods_name, price)VALUE(10, 'apple', 3000);SELECT * FROM `goods`

update语句

-- 演示update语句
-- 如果没有带where条件会修改所有的记录
UPDATE `employee` SET Salary = 5000;
SELECT * FROM `employee`;
UPDATE `employee`SET Salary = 3000WHERE user_name = 'whm';INSERT INTO `employee` VALUES (200, 'www', '1990-11-11', '2000-11-11', '后端', 5000, 'java', 'D:\\a.jpg');
DESC employeeUPDATE `employee`SET Salary = Salary + 1000, job = '全栈'WHERE user_name = 'www';

delete语句

-- DELETE 语句练习
DELETE FROM employeeWHERE user_name = 'www';SELECT * FROM employee;

select语句

-- select 语句（重点）
CREATE TABLE student(id INT NOT NULL DEFAULT 1,NAME VARCHAR(20) NOT NULL DEFAULT '',chinese FLOAT NOT NULL DEFAULT 0.0,english FLOAT NOT NULL DEFAULT 0.0,math FLOAT NOT NULL DEFAULT 0.0
);INSERT INTO student VALUES(1, 'a', 10, 20, 30);
INSERT INTO student VALUES(2, 'b', 10, 20, 30);
INSERT INTO student VALUES(3, 'c', 10, 20, 30);
INSERT INTO student VALUES(4, 'd', 10, 20, 30);
INSERT INTO student VALUES(5, 'e', 10, 20, 30);
INSERT INTO student VALUES(6, 'f', 10, 20, 30);SELECT * FROM student;SELECT `NAME`, english FROM student;-- 去重
SELECT DISTINCT english FROM student;

as

-- select语句的使用
-- 统计每个学生的总分
SELECT `name`, (chinese+english+math) FROM student;SELECT `name`, (chinese+english+math+10) FROM student;SELECT `name` as '名字', (chinese+english+math+10) AS total_score FROM student;

WHERE

-- select语句
SELECT * FROM studentWHERE `name` = 'a';SELECT * FROM studentWHERE english >= 20SELECT * FROM studentWHERE (chinese + math + english) >= 50SELECT * FROM studentWHERE math >= 20 AND id > 4SELECT * FROM studentWHERE english >= chinese AND id > 4SELECT * FROM studentWHERE (chinese + math + english) >= 50 and chinese < english and `name` LIKE    'a%'SELECT * FROM studentWHERE english BETWEEN 10 AND 20

order by like

-- 演示order by使用
-- 默认升序
SELECT * FROM studentORDER BY math;UPDATE student SET math = 20 WHERE id = 1;SELECT `name` , (chinese + english + math) AS total_score FROM studentORDER BY total_score DESC;SELECT `name` , (chinese + english + math) AS total_score FROM studentWHERE `name` like 'a%'ORDER BY total_score DESC;DESC student;
INSERT INTO student(id, `name`, chinese, english, math) VALUES (7, 'aa', 20, 30, 20);

COUNT SUM AVG MAX MIN

-- mysql统计函数的使用 COUNT SUM AVG MAX MIN
SELECT COUNT(*) FROM student;SELECT COUNT(*) FROM studentWHERE math > 20;SELECT COUNT(*) FROM studentWHERE (chinese + english + chinese) > 20;CREATE TABLE t15(`name` VARCHAR(20));
INSERT INTO t15 VALUES('tom');
INSERT INTO t15 VALUES('jack');
INSERT INTO t15 VALUES('mary');
INSERT INTO t15 VALUES(NULL);SELECT * FROM t15;SELECT COUNT(*) FROM t15;# 4SELECT COUNT(`name`) FROM t15;# 3SELECT SUM(math) FROM student;SELECT SUM(math) AS math_total_score, SUM(english), SUM(chinese) FROM student;SELECT SUM(math + english + chinese) FROM student;SELECT SUM(math) / count(*) FROM student;SELECT AVG(math) FROM student;SELECT AVG(math + english + chinese) FROM student;SELECT MAX(math + english + chinese), MIN(math + english + chinese) FROM student;SELECT MAX(math) AS math_high_score, MIN(math) AS math_low_score FROM student;

group by + having

-- 演示group by + having
CREATE TABLE dept(
deptno MEDIUMINT UNSIGNED NOT NULL DEFAULT 0,
dname VARCHAR(20) NOT NULL DEFAULT "",
loc VARCHAR(13) NOT NULL DEFAULT "");INSERT INTO dept VALUES(10, 'ACCOUNTING', 'NEW YORK'), (20, 'RESEARC', 'DALLAS'), (30, 'SALES', 'CHICAGO'), (40, 'OPERATIONS', 'BOSTON');SELECT * FROM dept;CREATE TABLE emp
(empno MEDIUMINT UNSIGNED NOT NULL DEFAULT 0,# /编号/
ename VARCHAR(20) NOT NULL DEFAULT "", #/名字/
job VARCHAR(9) NOT NULL DEFAULT "",#/工作/
mgr MEDIUMINT UNSIGNED ,#/上级编号/
hiredate DATE NOT NULL,#/入职时间/
sal DECIMAL(7,2) NOT NULL,#/薪水/
comm DECIMAL(7,2) ,#/红利 奖金/
deptno MEDIUMINT UNSIGNED NOT NULL DEFAULT 0 #/部门编号/);INSERT INTO emp VALUES(7369, 'SMITH', 'CLERK', 7902, '1990-12-17', 800.00,NULL , 20),
(7499, 'ALLEN', 'SALESMAN', 7698, '1991-2-20', 1600.00, 300.00, 30),
(7521, 'WARD', 'SALESMAN', 7698, '1991-2-22', 1250.00, 500.00, 30),
(7566, 'JONES', 'MANAGER', 7839, '1991-4-2', 2975.00,NULL,20),
(7654, 'MARTIN', 'SALESMAN', 7698, '1991-9-28',1250.00,1400.00,30),
(7698, 'BLAKE','MANAGER', 7839,'1991-5-1', 2850.00,NULL,30),
(7782, 'CLARK','MANAGER', 7839, '1991-6-9',2450.00,NULL,10),
(7788, 'SCOTT','ANALYST',7566, '1997-4-19',3000.00,NULL,20),
(7839, 'KING','PRESIDENT',NULL,'1991-11-17',5000.00,NULL,10),
(7844, 'TURNER', 'SALESMAN',7698, '1991-9-8', 1500.00, NULL,30),
(7900, 'JAMES','CLERK',7698, '1991-12-3',950.00,NULL,30),
(7902, 'FORD', 'ANALYST',7566,'1991-12-3',3000.00, NULL,20),
(7934,'MILLER','CLERK',7782,'1992-1-23', 1300.00, NULL,10);SELECT * FROM emp;#工资级别表CREATE TABLE salgrade(
grade MEDIUMINT UNSIGNED NOT NULL DEFAULT 0, /* 工资级别 */
losal DECIMAL(17,2) NOT NULL, /* 该级别的最低工资 */
hisal DECIMAL(17,2) NOT NULL /* 该级别的最高工资*/);INSERT INTO salgrade VALUES (1,700,1200);
INSERT INTO salgrade VALUES (2,1201,1400);
INSERT INTO salgrade VALUES (3,1401,2000);
INSERT INTO salgrade VALUES (4,2001,3000);
INSERT INTO salgrade VALUES (5,3001,9999);SELECT * FROM salgrade;SELECT AVG(sal), MAX(sal), deptno FROM empGROUP BY deptno;SELECT AVG(sal), MIN(sal), deptno, job FROM empGROUP BY deptno, job;-- 写法1
SELECT AVG(sal), deptno FROM empGROUP BY deptnohaving AVG(sal) < 2000-- 写法2
SELECT AVG(sal) AS avg_sal, deptno FROM empGROUP BY deptnohaving avg_sal < 2000

数学相关函数

-- 演示数学相关函数
-- 绝对值
SELECT ABS(-10) FROM DUAL;SELECT BIN(10) FROM DUAL;SELECT CEILING(-1.1) FROM DUAL;SELECT CONV(10,10,2) FROM DUAL;SELECT CONV(10,16,10) FROM DUAL;SELECT FLOOR(1.1) FROM DUAL;SELECT FORMAT(78.12345,4) FROM DUAL;SELECT LEAST(0.1,-1,4) FROM DUAL;SELECT MOD(10,2) FROM DUAL;SELECT RAND(3) FROM DUAL;

日期函数

-- 创建测试表
CREATE TABLE mes(id INT,content VARCHAR(30),send_time DATETIME);SELECT * FROM mes;INSERT INTO mes VALUES (1, "北京新闻", CURRENT_TIMESTAMP);INSERT INTO mes VALUES (2, "上海新闻", now());INSERT INTO mes VALUES (2, "广州新闻", now());UPDATE mes SET id = 3 WHERE content = "广州新闻";SELECT id, content, DATE(send_time) FROM mes;-- 查询10分钟内发布的新闻
SELECT * FROM mes WHERE DATE_ADD(send_time, INTERVAL 10 MINUTE) >= NOW();SELECT * FROM mes WHERE DATE_SUB(NOW(), INTERVAL 20 MINUTE) <= send_time;SELECT DATEDIFF('2011-11-11','1990-1-1') FROM DUAL;SELECT DATEDIFF(DATE_ADD('1986-11-11',INTERVAL 80 YEAR), NOW()) FROM DUAL;SELECT TIMEDIFF('10:11:11','06:10:10') FROM DUAL;SELECT YEAR(NOW()) FROM DUAL;
SELECT MONTH(NOW()) FROM DUAL;
SELECT DAY(NOW()) FROM DUAL;-- 返回1970-1-1到现在的秒数
SELECT UNIX_TIMESTAMP() FROM DUAL;
-- 意义：在开发中，可以存放一个整数，然后表示时间
SELECT FROM_UNIXTIME(1656850057, '%Y-%m-%d') FROM DUAL;SELECT FROM_UNIXTIME(1656850057, '%Y-%m-%d %H:%i:%s') FROM DUAL;

加密函数和系统函数

-- 查看当前登录到mysql有哪些用户
SELECT USER() FROM DUAL;-- 查询当前使用数据库名称
SELECT DATABASE() FROM DUAL;-- 加密md5
SELECT MD5('Whmhhh1998818!') FROM DUAL;
SELECT LENGTH(MD5('whm!')) FROM DUAL;DROP TABLE `user`;
CREATE TABLE `user`(id INT,NAME VARCHAR(32) NOT NULL DEFAULT "",pwd CHAR(32) NOT NULL DEFAULT "");INSERT INTO `user` VALUES(100, "whm", MD5('whm'));
SELECT * FROM `user`;SELECT *FROM `user`WHERE `name` = 'whm' and pwd = MD5('whm')SELECT PASSWORD('whm') FROM DUAL;SELECT * FROM mysql.`user`

流程控制语句

SELECT IF(TRUE,"北京","上海") FROM DUAL;SELECT IFNULL(NULL,"whm") FROM DUAL;SELECT CASEWHEN TRUE THEN'Jack'WHEN FALSE THEN'Tom'ELSE'mary'
END CASE;SELECT ename, IF(comm IS NULL, 0.0, comm)FROM emp;SELECT ename, IFNULL(comm, 0.0)FROM emp;SELECT ename, (SELECT CASEWHEN job = 'CLERK' THEN'职员'WHEN job = 'MANAGER' THEN'经理'ELSE'销售人员'
END) AS 'job'FROM emp;

查询加强

SELECT * FROM empWHERE hiredate > "1992-01-01"-- %表示0到多个任意字符 _表示单个任意字符
SELECT ename, sal FROM empWHERE ename LIKE 'S%'SELECT ename, sal FROM empWHERE ename LIKE '__O%'SELECT * FROM empWHERE mgr IS NULL;DESC emp;SELECT * FROM empORDER BY salSELECT * FROM empORDER BY deptno ASC, sal DESC

分页查询

SELECT * FROM empORDER BY empnoLIMIT 0, 3;SELECT * FROM empORDER BY empnoLIMIT 3, 3;SELECT * FROM empORDER BY empnoLIMIT 6, 3;SELECT * FROM empORDER BY empnoLIMIT 9, 3;SELECT * FROM empORDER BY empnoLIMIT 12, 3;

增强group by使用

SELECT COUNT(*), AVG(sal), jobFROM empGROUP BY job;SELECT COUNT(*), COUNT(comm)FROM emp;SELECT COUNT(*), COUNT(IF(comm IS NULL, 1, NULL))FROM emp;SELECT COUNT(*), COUNT(*) - COUNT(comm)FROM emp;SELECT COUNT(DISTINCT(mgr))FROM emp;SELECT MAX(sal) - MIN(sal)FROM emp;# 注意顺序
SELECT deptno, AVG(sal) AS avg_salFROM empGROUP BY deptnoHAVING avg_sal > 1000ORDER BY avg_sal DESCLIMIT 0, 2;

多表查询

SELECT * FROM emp;
SELECT * FROM dept;
SELECT * FROM emp, dept;SELECT ename, sal, dname, dept.deptno FROM emp, deptWHERE emp.deptno = dept.deptno;SELECT ename, sal, dname, dept.deptno FROM emp, deptWHERE emp.deptno = dept.deptno AND dept.deptno = 10;SELECT ename, sal, grade FROM emp, salgradeWHERE emp.sal BETWEEN salgrade.losal AND salgrade.hisal;

自连接

-- 多表查询的自连接
-- 显示公司员工名称和他上级的名字
SELECT worker.ename AS '职工名', boss.ename AS '上级名'FROM emp AS worker, emp AS bossWHERE worker.mgr = boss.empno;

子查询演示 IN关键字

-- smith同一个部门的
SELECT deptno FROM empWHERE ename = 'SMITH';SELECT * FROM empWHERE deptno = (SELECT deptno FROM empWHERE ename = 'SMITH');SELECT DISTINCT(job) FROM empWHERE deptno = 10;SELECT ename, job, sal, deptno FROM empWHERE job in (SELECT DISTINCT(job) FROM empWHERE deptno = 10) AND deptno != 10;

any 和 all关键字

SELECT ename, sal, deptnoFROM empWHERE sal > (SELECT MAX(sal) FROM emp WHERE deptno=30);SELECT ename, sal, deptnoFROM empWHERE sal > ALL(SELECT sal FROM emp WHERE deptno=30);SELECT ename, sal, deptnoFROM empWHERE sal > ANY(SELECT sal FROM emp WHERE deptno=30);

多列子查询

SELECT deptno, jobFROM empWHERE ename = "SMITH"SELECT * FROM empWHERE (deptno, job) = (SELECT deptno, jobFROM empWHERE ename = "SMITH") AND ename != "SMITH";SELECT * FROM empWHERE deptno = (SELECT deptnoFROM empWHERE ename = "SMITH" )AND job = (SELECT jobFROM empWHERE ename = "SMITH" );

子查询练习

SELECT deptno, AVG(sal) FROM empGROUP BY deptno;SELECT ename, sal, temp.avg_sal, emp.deptno FROM emp, (SELECT deptno, AVG(sal) AS avg_sal FROM empGROUP BY deptno) AS tempWHERE emp.deptno = temp.deptno AND emp.sal > temp.avg_sal;SELECT ename, sal, temp.max_sal, emp.deptno FROM emp, (SELECT deptno, MAX(sal) AS max_sal FROM empGROUP BY deptno) AS tempWHERE emp.deptno = temp.deptno AND emp.sal = temp.max_sal;SELECT dname, temp.deptno, loc, temp.pALL FROM (SELECT deptno, count(*) AS pALL FROM emp GROUP BY deptno) AS temp, deptWHERE temp.deptno = dept.deptno;
-- 或
SELECT temp.*, dname, loc FROM (SELECT deptno, count(*) AS pALL FROM emp GROUP BY deptno) AS temp, deptWHERE temp.deptno = dept.deptno;

表的复制

CREATE table my_table01(id INT,`name` VARCHAR(32),sal DOUBLE,job VARCHAR(32),deptno INT);SELECT * FROM my_table01;INSERT INTO my_table01 (id, `name`, sal, job, deptno) SELECT empno, ename, sal, job, deptno FROM emp;-- 自我复制 成指数次增长
INSERT INTO my_table01 SELECT * FROM my_table01;-- 删除一张表重复数据
CREATE TABLE my_table02 LIKE emp;# 这个语句把emp表结构 复制到my_table02SELECT * FROM my_table02;INSERT INTO my_table02 SELECT * FROM emp;CREATE TABLE my_tmp LIKE my_table02;INSERT INTO my_tmp SELECT DISTINCT * FROM my_table02;DELETE FROM my_table02;INSERT INTO my_table02 SELECT * FROM my_tmp;DROP TABLE my_tmp;SELECT * FROM my_table02;

合并查询

SELECT ename, sal, job FROM emp WHERE sal > 2500;SELECT ename, sal, job FROM emp WHERE job = "MANAGER";-- UNION ALL合并不会去除
SELECT ename, sal, job FROM emp WHERE sal > 2500
UNION ALL
SELECT ename, sal, job FROM emp WHERE job = "MANAGER";-- UNION合并会去除
SELECT ename, sal, job FROM emp WHERE sal > 2500
UNION
SELECT ename, sal, job FROM emp WHERE job = "MANAGER";SELECT ename, sal, job FROM emp WHERE sal > 2500 OR job = "MANAGER";

外连接

SELECT dname, ename, job FROM emp, deptWHERE emp.deptno = dept.deptnoORDER BY dname;CREATE TABLE stu(
id INT,
`name` VARCHAR(32));INSERT INTO stu VALUES(1, "Jack"),(2, "tom"), (3, "kitty"), (4, "nono");SELECT * FROM stu;CREATE TABLE exam(
id INT,
grade INT);INSERT INTO exam VALUES(1, 56),(2, 76), (11, 8);SELECT * FROM exam;SELECT `name`, stu.id, grade FROM stu, exam WHERE stu.id = exam.id;--  改成左外链接SELECT `name`, stu.id, grade FROM stu LEFT JOIN exam ON stu.id = exam.id;--    改成右外链接SELECT `name`, stu.id, grade FROM stu RIGHT JOIN exam ON stu.id = exam.id;SELECT dname, ename FROM dept LEFT JOIN empON dept.deptno = emp.deptno;

主键使用

CREATE TABLE t17(id INT PRIMARY KEY,`name` VARCHAR(32),email VARCHAR(32));-- 主键不能重复，且不能为空
INSERT INTO t17 VALUES(1, 'jack', "1"),(2, "tom", "2"),(1, "whm", "3");SELECT * FROM t17;CREATE TABLE t18(id INT PRIMARY KEY,`name` VARCHAR(32) PRIMARY KEY, # 错误email VARCHAR(32));-- 复合主键
CREATE TABLE t18(id INT,`name` VARCHAR(32),email VARCHAR(32),PRIMARY KEY(id, `name`));INSERT INTO t18 VALUES(1, 'jack', "1"),(1, "whm", "3");
INSERT INTO t18 VALUES(1, 'jack', "4");DESC t18;

unique的使用

CREATE TABLE t19(id INT UNIQUE, # 表示id列是不可以重复的`name` VARCHAR(32),email VARCHAR(32));INSERT INTO t19 VALUES(1, 'jack', "1"),(1, "whm", "3");-- 如果没要指定not null则 unique 字段可以有多个null
INSERT INTO t19 VALUES(NULL, 'jack', "1"),(NULL, "whm", "3"), (NULL, 'jack', "4");SELECT * FROM t19;-- 一张表可以有多个unique
-- unique + not null = PRIMARY KEY

外键演示

CREATE TABLE my_class(id INT PRIMARY KEY,`name` VARCHAR(32) NOT NULL DEFAULT " ");CREATE TABLE my_stu(id INT PRIMARY KEY,`name` VARCHAR(32) NOT NULL DEFAULT " ",class_id INT,FOREIGN KEY (class_id) REFERENCES my_class(id));INSERT INTO my_class VALUES(100, "java"), (200, "web");INSERT INTO my_stu VALUES(1, "tom", 100), (2, "jack", 200), (3, "whm", 300);SELECT * FROM my_stu;

演示check的使用

-- mysql15.7还不支持check，只做语法校验，但不会生效
CREATE TABLE t20(id INT PRIMARY KEY,`name` VARCHAR(32),sex VARCHAR(6) CHECK (sex IN('man', 'woman')),sal DOUBLE CHECK (sal > 1000 AND sal < 2000));INSERT INTO t20 VALUES(1, "jack", "mid", 1);SELECT * FROM t20;

使用约束建表

CREATE DATABASE shop_db;CREATE TABLE goods(
​   goods_id INT PRIMARY KEY,
​   goods_name VARCHAR(64) NOT NULL DEFAULT "",
​   unitprice DECIMAL(10, 2) NOT NULL DEFAULT 0
​       CHECK (unitprice >= 1.0 AND unitprice <= 9999.99),
​   category INT NOT NULL DEFAULT 0,
​   provider VARCHAR(64) NOT NULL DEFAULT "");
​
CREATE TABLE customer(
​   customer_id CHAR(8) PRIMARY KEY,
​   `name` VARCHAR(64) NOT NULL DEFAULT "",
​   address VARCHAR(64) NOT NULL DEFAULT "",
​   emil VARCHAR(64) NOT NULL DEFAULT "",
​   sex ENUM('男', '女') NOT NULL,
​   card_Id CHAR(18));
​
CREATE TABLE purchase(
​   order_id INT UNSIGNED PRIMARY KEY,
​   customer_id CHAR(18) NOT NULL DEFAULT "",
​   goods_id INT NOT NULL DEFAULT 0,
​   nums INT NOT NULL DEFAULT 0,
​   FOREIGN KEY (customer_id) REFERENCES customer(customer_id),
​   FOREIGN KEY (goods_id) REFERENCES goods(goods_id));
​
DESC goods;
DESC customer;
DESC purchase;

演示自增长的使用

-- AUTO_INCREMENT只能修饰PRIMARY KEY或unique值
CREATE TABLE t21(id INT PRIMARY KEY AUTO_INCREMENT,email VARCHAR(32) NOT NULL DEFAULT " ",`name` VARCHAR(32) NOT NULL DEFAULT " ");DESC t21;INSERT INTO t21 VALUES(NULL, 'jack', "jack");INSERT INTO t21 VALUES(NULL, 'tom', "tom");INSERT INTO t21(email, `name`) VALUES('ketty', "ketty");SELECT * FROM t21;CREATE TABLE t22(id INT PRIMARY KEY AUTO_INCREMENT,email VARCHAR(32) NOT NULL DEFAULT " ",`name` VARCHAR(32) NOT NULL DEFAULT " ");-- 自增长从100开始
ALTER TABLE t22 AUTO_INCREMENT 100;INSERT INTO t22 VALUES(NULL, 'jack', "jack");SELECT * FROM t22;

演示mysql索引的使用

CREATE TABLE t23(id INT,`name` VARCHAR(32));
-- 查询索引
SHOW INDEX FROM t23;
SHOW KEYS FROM t23;
-- 添加唯一索引
CREATE UNIQUE INDEX id_index ON t23(id);
-- 添加普通索引方法一
CREATE INDEX id_index ON t23(id);
-- 添加普通索引方法二
ALTER TABLE t23 ADD INDEX id_index(id);CREATE TABLE t24(id INT,`name` VARCHAR(32));
ALTER TABLE t24 ADD PRIMARY KEY id_index(id);SHOW INDEX FROM t24;-- 删除索引
DROP INDEX id_index ON t23;ALTER TABLE t24 DROP PRIMARY KEY;

事务的概念

CREATE TABLE t25(id INT,`name` VARCHAR(32));--     开始事务
START TRANSACTION;
-- 设置保存点
SAVEPOINT a;INSERT INTO t25 VALUES (100, "tom");SAVEPOINT b;INSERT INTO t25 VALUES (200, "jack");SELECT * FROM t25;ROLLBACK TO b;ROLLBACK TO a;ROLLBACK;INSERT INTO t25 VALUES(300, 'milan'); # 自动commitROLLBACK;START TRANSACTION;SET autocommit = off;INSERT INTO t25 VALUES(400, 'king');INSERT INTO t25 VALUES(500, 'scott');ROLLBACK; # 直接回退到事务开始的地方

演示mysql的事务隔离级别

SELECT @@tx_isolation
SELECT @@global.tx_isolation-- +-----------------+
-- | @@tx_isolation  |
-- +-----------------+
-- | REPEATABLE-READ |
-- +-----------------+-- 把其中一个控制台的隔离级别设置 Read UNCOMMITTEDSET SESSION TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
SET GLOBAL TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;CREATE TABLE `account`(id INT,`name` VARCHAR(32),money INT);-- +----------------+
-- | @@tx_isolation |
-- +----------------+
-- | READ-COMMITTED |
-- +----------------+-- +-----------------+
-- | @@tx_isolation  |
-- +-----------------+
-- | REPEATABLE-READ |
-- +-----------------+-- +----------------+
-- | @@tx_isolation |
-- +----------------+
-- | SERIALIZABLE   |
-- +----------------+

表类型和存储引擎

-- 查看所有的引擎
SHOW ENGINES;-- INNODB 支持事务/支持外键/支持行级锁-- MYISAM 添加速度快 不支持外键和事务 支持表级锁
CREATE TABLE t26(
​   id INT,
​   `name` VARCHAR(32)) ENGINE MYISAM;
​
START TRANSACTION;SAVEPOINT t1;
INSERT INTO t26 VALUES(1, 'jack');
SELECT * FROM t26;
ROLLBACK TO t1;-- memory 数据存储在内存中 执行速度很快 内存中没要io 默认支持索引 hash
CREATE TABLE t27(
​   id INT,
​   `name` VARCHAR(32)) ENGINE MEMORY;
INSERT INTO t27 VALUES(1, 'jack'), (2, 'tom'), (3, 'hsp');
SELECT * FROM t27;-- 指令修改存储引擎
ALTER TABLE t27 ENGINE = INNODB;

视图

1.视图是根据基表（可以是多个基表）来创建的视图是虚拟的表

2.视图也有列，数据来自基表

3.通过视图可以修改基表的数据

4.基表的改变，也会影响视图的数据

-- 视图的使用
CREATE VIEW emp_view01ASSELECT empno, ename, job, deptno FROM emp;DESC emp_view01;SELECT * FROM emp_view01;SELECT empno, job FROM emp_view01;SHOW CREATE VIEW emp_view01;DROP VIEW emp_view01;-- 修改视图会影响基表
UPDATE emp_view01SET job = 'MANAGER'WHERE empno = 7369UPDATE empSET job = 'SALESMAN'WHERE empno = 7369CREATE VIEW emp_view02ASSELECT empno, ename FROM emp_view01;SELECT * FROM emp_view02;

用户权限管理

CREATE USER 'member01'@'localhost' IDENTIFIED BY '123';CREATE DATABASE testdb;
CREATE TABLE news(
​   id INT,
​   content VARCHAR(32));
INSERT INTO news VALUES (100, '北京新闻');GRANT SELECT, INSERT
​   ON testdb.news
​   TO 'member01'@'localhost';
​
GRANT UPDATE
​   ON testdb.news
​   TO 'member01'@'localhost';
​
SET PASSWORD FOR 'member01'@'localhost' = PASSWORD('abc');
-- 回收所有权限
REVOKE ALL ON testdb.news FROM 'member01'@'localhost';DROP USER 'member01'@'localhost';-- 用户权限管理
CREATE USER 'member01'@'localhost' IDENTIFIED BY '123';CREATE DATABASE testdb;
CREATE TABLE news(
​   id INT,
​   content VARCHAR(32));
INSERT INTO news VALUES (100, '北京新闻');GRANT SELECT, INSERT
​   ON testdb.news
​   TO 'member01'@'localhost';
​
GRANT UPDATE
​   ON testdb.news
​   TO 'member01'@'localhost';
​
SET PASSWORD FOR 'member01'@'localhost' = PASSWORD('abc');
-- 回收所有权限
REVOKE ALL ON testdb.news FROM 'member01'@'localhost';DROP USER 'member01'@'localhost';CREATE USER 'member01'@'192.168.1.%' IDENTIFIED BY '123';

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