Free recommendation: mysql video tutorial
Select Operating System:Microsoft Windows
Quick download: mysql-8.0.22-winx64.zip
MYSQL_HOME: C:\MySQL\mysql-8.0.22-winx64
my.ini configuration file in the root directory of the decompression [mysqld] #设置3306端口 port = 3306 # 设置mysql的安装目录 basedir=C:/MySQL/mysql-8.0.22-winx64 # 设置mysql数据库的数据的存放目录 datadir=C:/MySQL/mysql-8.0.22-winx64\data # 允许最大连接数 max_connections=200 # 允许连接失败的次数。这是为了防止有人从该主机试图攻击数据库系统 max_connect_errors=10 # 服务端使用的字符集默认为utf8 character-set-server=utf8mb4 # 创建新表时将使用的默认存储引擎 default-storage-engine=INNODB # 默认使用 “mysql_native_password” 插件认证 default_authentication_plugin=mysql_native_password [mysql] # 设置mysql客户端默认字符集 default-character-set=utf8mb4 [client] # 设置mysql客户端连接服务端时默认使用的端口 port=3306 # 设置mysql客户端连接服务端时默认使用的字符集 default-character-set=utf8mb4
mysqld --defaults-file=C:\MySQL\mysql-8.0.22-winx64\my.ini --initialize --console
Note: Copy and save the MySQL initialization passwordfVdpg:bM9pAk
mysqld --install mysql8
net start mysql8
mysql -u账号 -p密码
Solution for failing to log in using the above method
1. Stop mysql8
net stop mysql82. Passwordless startup
mysqld --console --skip-grant-tables --shared-memory3. The previous window cannot be closed, and then open a new window. Login without password
mysql -u root -p4. Clear password
update mysql.user set authentication_string='' where user='root' and host='localhost;'5. Refresh privilege
plush privilege;6. Restart the mysql service, and then log in to mysql without password
ALTER USER root@localhost IDENTIFIED BY '123456';
CREATE USER 'root' @'%' IDENTIFIED BY '123456'; -- 这一步执行失败也没关系 GRANT ALL ON *.* TO 'root' @'%'; # alter user 'root'@'%' identified with mysql_native_password by '123456'; FLUSH privilege;
Select Operating System:Source Code
Select OS Version:Generic Linux (Architecture Independent)
Quick download: mysql-8.0.22.tar.gz
mysql-8.0.22 .tar.gz
tar -zxvf mysql-8.0.22.tar.gz
mv mysql-8.0.22 /usr/local/mysql
groupadd mysql useradd -r -g mysql mysql
/usr/local/mysql directory and modify the relevant permissionscd /usr/local/mysql chown -R mysql:mysql ./
cd /usr/local/mysql/bin ./mysqld --initialize --user=mysql --basedir=/usr/local/mysql --datadir=/usr/local/mysql/data
Note: Copy and save the MySQL initialization passwordfVdpg:bM9pAk
/etc/my.cnf
cd /etc vi my.cnf
my.cnf
[mysqld] port = 3306 basedir=/usr/local/mysql datadir=/usr/local/mysql/data max_connections=200 max_connect_errors=10 character-set-server=utf8mb4 default-storage-engine=INNODB default_authentication_plugin=mysql_native_password [mysql] default-character-set=utf8mb4 [client] port=3306 default-character-set=utf8mb4
cd /usr/local/mysql/support-files ./mysql.server start
cd /usr/local/mysql/bin ./mysql -u root -p生成的临时密码 ALTER USER 'root' @'localhost' IDENTIFIED BY '123456';
CREATE USER 'root' @'%' IDENTIFIED BY '123456'; -- 这一步执行失败也没关系 GRANT ALL ON *.* TO 'root' @'%'; FLUSH privilege;
Create database
CREATE DATABASE db_name DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci;
Query database
-- 查询所有数据库 SHOW DATABASES; -- 查询数据库建表时的sql脚本 SHOW CREATE DATABASE db_name;
Delete database
DROP DATABASE db_name;
Modify database
-- 修改数据库的字符编码和排序方式 ALTER DATABASE db_name DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci;
Select database
USE db_name;
Set the encoding format of the operation
SET NAMES utf8;
CREATE TABLE tb_name (field to create table , type, length, constraint, default, comment)
Constraint
NOT NULL
UNSIGNED
PRIMARY KEY
AUTO_INCREMENT
DEFAULT
COMMENT
-- 数据库存在就删除 DROP DATABASE IF EXISTS testdb; -- 创建数据库的操作 CREATE DATABASE IF NOT EXISTS testdb; -- 使用数据库 USE testdb; -- 数据表存在就删除 DROP TABLE IF EXISTS testdb; -- 创建表的操作 CREATE TABLE IF NOT EXISTS tb_test ( test_id INTEGER ( 10 ), test_name VARCHAR ( 50 ) );
-- 使用数据库 USE testdb; -- 数据表存在就删除 DROP TABLE IF EXISTS testdb; -- 创建表的操作 CREATE TABLE IF NOT EXISTS tb_test ( test_id INTEGER (10) AUTO_INCREMENT PRIMARY KEY COMMENT '测试ID', test_name VARCHAR (50) NOT NULL COMMENT '测试名称', test_password VARCHAR(20) NOT NULL DEFAULT '123456' COMMENT '测试密码' );
Common types
TIYINT 1个字节，无符号最大值 256 (2^8 -1)，正负 -128 ~ 127 (-2^7 -1 ~ 2^7 -1)SMALLINT 2个字节，无符号最大值 65535 (2^16 - 1)，正负 -32768 ~ 32767 (-2^15 - 1 ~ 2^15 - 1)MEDIUMINT 3个字节，无符号最大值 16777215 (2^24 - 1)，正负 (-2^23-1 ~ 2^23-1)INT 4个字节，无符号最大值 2^32 -1，正负 (-2^31-1 ~ 2^31-1)BIGINT 8个字节，无符号最大值 2^64 - 1, 正负 (-2^63-1 ~ 2^63-1)FLOAT 4个字节 Float [(M,D)] -3.4E+38~3.4E+38( 约 )DOUBLE 8个字节 Double [(M,D)] -1.79E+308~1.79E+308( 约 )DECIMAL M>D ? M+2 : D+2 个字节 Decimal [(M,D)] 注：M 为长度， D 为小数CHAR 最大保存255个字节，如果值没有达到给定的长度，使用空格补充VARCHAR 最大保存255个字节，用多大长度占多大长度TINYTEXT 最大长度255个字节(2^8-1)MEDIUMTEXT 最大长度 16777215 个字节(2^24-1)TEXT 最大长度65535个字节(2^16-1)LONGTEXT 最大长度4294967295个字节 (2^32-1)DATE 日期(yyyy-mm-dd)TIME 时间(hh:mm:ss)DATETIME 日期与时间组合(yyyy-mm-dd hh:mm:ss)TIMESTAMP yyyymmddhhmmssYEAR 年份yyyy-- 创建表的操作 CREATE TABLE IF NOT EXISTS tb_user ( user_id int(11) AUTO_INCREMENT PRIMARY KEY COMMENT '用户ID', user_name VARCHAR (30) NOT NULL COMMENT '用户名称', user_birthday date COMMENT '用户生日', user_gender CHAR(3) COMMENT '用户性别', user_status TINYINT(1) NOT NULL COMMENT '用户状态', user_height DECIMAL(4,1) NOT NULL COMMENT '用户身高', user_desc text COMMENT '用户简介' );
表字段索引
table_name ADD PRIMARY KEY (column)，用于唯一标识一条记录table_name ADD UNIQUE (column) 往往不是为了提高访问速度，而是为了避免数据出现重复table_name ADD INDEX index_name (column)，唯一任务是加快对数据的访问速度table_name ADD FULLTEXT index_name (column1, column2) ，仅可用于 MyISAM 表，针对较大的数据，生成全文索引很耗时好空间table_name ADD INDEX index_name (column1, column2, column3) ，为了更多的提高mysql效率# 删除主键索引 ALTER TABLE `table_name` DROP PRIMARY KEY # 删除唯一索引 ALTER TABLE `table_name` DROP INDEX unique_index_name; ALTER TABLE `table_name` DROP INDEX cloumn; # 删除普通索引 ALTER TABLE `table_name` DROP INDEX index_name; # 删除全文索引 ALTER TABLE `table_name` DROP INDEX fulltext_index_name; ALTER TABLE `table_name` DROP INDEX cloumn;
字段添加
# ALTER TABLE tb_name ADD 字段 字段类型 非空约束 默认值 注释 ALTER TABLE tb_name ADD address VARCHAR ( 100 ) NOT NULL DEFAULT COMMENT '用户地址';
字段类型修改
# ALTER TABLE tb_name MODIFY 字段 新的字段类型 非空约束 默认值 注释 ALTER TABLE tb_name MODIFY address VARCHAR ( 50 ) NOT NULL DEFAULT COMMENT '用户地址';
字段名称类型修改
# ALTER TABLE tb_name MODIFY 旧的字段 新的字段 新的字段类型 非空约束 默认值 注释 ALTER TABLE tb_name CHANGE address addr VARCHAR ( 50 ) NOT NULL DEFAULT COMMENT '用户地址';
字段类型查询
DESC tb_name;
字段删除
# ALTER TABLE tb_name DROP 字段 ALTER TABLE tb_name DROP addr;
表名修改
# ALTER TABLE 旧表名 RENAME TO 新表名 ALTER TABLE tb_name RENAME TO tb_name1
表引擎修改
# ALTER TABLE tb_name ENGINE = 新引擎 ALTER TABLE tb_name ENGINE = MyISAM;
# DROP TABLE 表名 DROP TABLE tb_name; # 如果表存在就删除 DROP TABLE IF EXISTS tb_name;
# 查询所有表 SHOW TABLES; # 查询建表时的脚本 SHOW CREATE TABLE tb_name;
# insert into 表名 (字段名：字段1,字段2,...字段n) values (值1,值2,...值n);
# 全表插入
INSERT INTO `tb_user`(`user_name`, `user_birthday`, `user_gender`, `user_status`, `user_height`, `user_desc`) VALUES ('曾小贤', '2020-11-22', '男', 1, 174.5, '好男人就是我，我就是好男人曾小贤');
# 指定列插入，前提是其他列没有非空的约束
INSERT INTO `tb_user`(`user_name`, `user_birthday`, `user_gender`, `user_status`, `user_height`) VALUES ('胡小梅', '2020-11-22', '女', 1, 174.5);
# update 表名 set 字段1=新值1,字段2=新值2,...字段n=新值n where 条件 UPDATE `tb_user` SET user_birthday='1995-10-20' WHERE user_id=2; UPDATE `tb_user` SET user_birthday='1995-10-20', user_status = 2 WHERE user_id=2; UPDATE `tb_user` SET user_status = 1 where user_id > 1; UPDATE `tb_user` SET user_status = 1;
# delete from 表名 where 条件 DELETE FROM `tb_user` WHERE user_id=2;
# select 字段1,字段2,...字段n from 表名 where 条件 # 不带条件查询 select * from tb_user; select user_id,user_name from tb_user; # 带条件查询 (比较运算 >, <, >=, <=, !=, <>, =) select * from tb_user where user_id > 1; # 带逻辑条件查询 (and,or) select * from tb_user where user_status = 1 and user_id > 1; select * from tb_user where user_id = 1 or user_name = '胡小梅'; # 模糊查询 (like %%) select * from tb_user where user_name like '曾%'; select * from tb_user where user_name like '%闲'; select * from tb_user where user_name like '%小%'; # 范围查询 select * from tb_user where tb_status in (0,1,2); # 聚合函数 -- count(field) select count(user_id) 用户数量 from tb_user; -- sum(field) select sum(user_height) 总身高 from tb_user; -- avg(field) select avg(user_height) 平均身高 from tb_user; ... # 分组查询 -- group by 统计男女的平均身高: group by 查询中出现的字段必须是 group by 后面的字段 select user_gender as 性别,avg(user_height) 平均身高 from tb_user group by user_gender; select user_status,user_gender as 性别,avg(user_height) 平均身高 from tb_user group by user_gender,user_status; select user_gender as 性别,avg(user_height) 平均身高,sum(user_height),count(user_id) 用户数量 from tb_user group by user_gender; # 排序查询 -- order by 默认是 asc 升序, desc 降序; order by 是放在 group by 之后的 select * from tb_user order by user_id asc; select * from tb_user order by user_id desc; select * from tb_user where user_id < 10 order by user_id desc; select * from tb_user where user_id < 10 order by user_id,user_status desc; select user_gender as 性别,avg(user_height) 平均身高,sum(user_height),count(user_id) 用户数量 from tb_user group by user_gender order by 用户数量;
# 创建分数表 CREATE TABLE `tb_score` ( `id` int(11) NOT NULL PRIMARY KEY AUTO_INCREMENT, `stu_id` int(11) NOT NULL, `cou_id` int(11) NOT NULL, `score` decimal(4,1) NOT NULL ); -- 插入测试数据 INSERT INTO tb_score (`stu_id`, `cou_id`, `score`) VALUES(1,1,89.0); INSERT INTO tb_score (`stu_id`, `cou_id`, `score`) VALUES(1,2,78.0); INSERT INTO tb_score (`stu_id`, `cou_id`, `score`) VALUES(1,3,94.0); INSERT INTO tb_score (`stu_id`, `cou_id`, `score`) VALUES(1,4,77.0); INSERT INTO tb_score (`stu_id`, `cou_id`, `score`) VALUES(1,5,99.0); INSERT INTO tb_score (`stu_id`, `cou_id`, `score`) VALUES(3,1,90.0); INSERT INTO tb_score (`stu_id`, `cou_id`, `score`) VALUES(3,2,88.0); INSERT INTO tb_score (`stu_id`, `cou_id`, `score`) VALUES(3,3,69.0); INSERT INTO tb_score (`stu_id`, `cou_id`, `score`) VALUES(3,4,83.0); INSERT INTO tb_score (`stu_id`, `cou_id`, `score`) VALUES(3,5,92.0); INSERT INTO tb_score (`stu_id`, `cou_id`, `score`) VALUES(2,1,77.0); INSERT INTO tb_score (`stu_id`, `cou_id`, `score`) VALUES(2,2,84.0); INSERT INTO tb_score (`stu_id`, `cou_id`, `score`) VALUES(2,3,91.0); INSERT INTO tb_score (`stu_id`, `cou_id`, `score`) VALUES(2,4,80.0); INSERT INTO tb_score (`stu_id`, `cou_id`, `score`) VALUES(2,5,99.0); # 分页查询 -- 查询科目id为1的最高成绩 select max(score) from tb_score where course_id = 1; select * from tb_score where course_id = 1 limit 1; -- 查询课程id为4的前五名成绩信息 select * from tb_score where course_id = 4 order by score limit 5; -- limit 分页, 起始值是 0： (pageIndex - 1) * pageSize, pageSize select * from tb_score limit 0,10 select * from tb_score limit 10,10 select * from tb_score limit 20,10
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