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MySQL基础命令

时间:2019-10-19 13:17:31      阅读:92      评论:0      收藏:0      [点我收藏+]

标签:ldb   表结构   路径   foreign   lint   最小   添加   数值   index   

查看当前所在库;

select database();

创建gamedb库;

create database gamedb;

切换到gamedb库;

use gamedb;

查看gamedb库里的表;

show tables;

创建gamedbinfo表;

create table gamedb.gamedbinfo(name char(10),age int);

use gamedb;

show tables;

查看gamedbinfo表结构;

desc gamedb.gamedbinfo; (desc后跟绝对路径,如果查询当前库里的表结构,则可以使用相对路径,如:desc gamedbinfo;)

查看 gamedb库里gamedbinfo表所有内容;

select * from gamedb.gamedbinfo;

插入表记录;

insert into gamedb.gamedbinfo values("Tom",22),("Maria",33);

修改表记录;

update gamedb.gamedbinfo set age=19 where name="Tom"; (修改Tom的记录)
update gamedb.gamedbinfo set age=19 (修改所有记录)

查看表所有内容;

select * from gamedb.gamedbinfo;

删除表记录;

delete from gamedb.gamedbinfo where name="Tom"; (删除Tom的记录)

delete from gamedb.gamedbinfo; (删除表中所有记录)

删除表;

drop table gamedb.gamedbinfo;

删除库;

drop database gamedb;

添加字段;

alter table T4 add email varchar(30) default "stu@tedu.cn";

alter table T4 add tel char(11);

alter table T4 add stu_num char(9) first;

alter table T4 add class char(7) default "nsd1808" after name;

修改字段类型,约束条件

alter table T4 modify stu_num varchar(10);

alter table T4 modify age tinyint default 25;

alter table T4 modify age tinyint default 25 after name;

alter table T4 modify likes set(‘eat‘,‘sleep‘,‘game‘,‘zhang‘,‘it‘,‘book‘) null default "it,book";

修改字段名;

alter table T4 change email mail varchar(30) default "stu@tedu.cn";

删除字段:

alter table T4 drop mail;

修改表名:

alter table T4 rename stutab;

创建index索引:

create index name on T3(name);

desc T3;

show index from T3;

drop index name on T3;

create table T4 (
name char(10) not null,
age tinyint not null default 25,
likes set("eat","sleep","game","zhang")
default "eat,sleep",
index(name),index(age)
);

desc T4;

show index from T4;

创建主键(primary key)

方法一:
create table T5(
name char(5),
class char(7),
stu_num char(9),
primary key(stu_num)
);

方法二:
create table T6(
name char(5),
class char(7),
stu_num char(9) primary key
);

创建复合主键:

create table T6(
clientip char(15),
serport smallint unsigned,
status enum("allow","deny"),
primary key(clientip,serport)
);

删除主键:

alter table T6 drop primary key;

在已有表里创建主键:

alter table T6 add primary key(serport,clientip);

与 AUTO_INCREMENT 连用 让字段的值自动增长:
数值类型
必须是primary key

create table T7(
id int primary key auto_increment,
name char(10),
age tinyint
);

删除id字段自增长功能:

alter table T7 modify id int not null;

创建外键:

create table yg(
yg_id int primary key auto_increment,
name char(10)
)engine=innodb;

create table gz(
gz_id int,
pay float(7,2)
foreign key(gz_id) references yg(yg_id)
on uptade cascade on delete cascade
)engine=innodb;

查看建表的过程:

show create table gz;

同步更新:

update yg set yg_id=8 where yg_id=2;

同步删除:

delete from yg where yg_id=1;

设置默认存储引擎:
修改/etc/my.cnf配置文件
default-storage-engine=存储引擎名称

vim /etc/my.cnf
[mysqld]
default-storage-engine=myisam

查询user表里name字段的个数:

select count(name) from user;

查询user表里name字段当其shell不等于/bin/bash的个数:

select count(name) from user where shell!="/bin/bash";

查询user表里,最小uid号码:

select min(uid) from user;

查询user表里,最小uid号码,当uid号<1000

select min(uid) from user where uid<=1000;

查询结果排序:

select name,uid from user order by uid; (升序)
select name,uid from user order by uid desc; (降序)

查询结果分组:

select gid from user group by gid;
select shell from user group by shell;
select shell from user where uid>10 and uid<=2000 group by shell;

数据完全备份:mysqldump

mkdir /mydata
mysqldump -uroot -p123456 -A > /mydata/alldb.sql

备份db4库数据:

mysqldump -uroot -p123456 db4 > /mydata/db4.sql

备份db4库里的t2表:

mysqldump -uroot -p123456 db4 t2 > /mydata/db4_t2.sql

同时备份多个库:

mysqldump -uroot -p123456 -B db3 db2 > /mydata/twodb.sql

完全恢复数据()删除对应的备份数据,然后使用备份文件恢复数据:

mysql -uroot -p123456 db4 < /mydata/db4_t2.sql
mysql -uroot -p123456 db4 < /mydata/db4.sql

启用binlog日志,进行实时增量备份:

binlog日志介绍?

启用日志文件:

vim /etc/my.cnf
[mysqld]
#log_bin
log_bin=/logdir/plj
server_id=50
binlog_format="mixed"
:wq

mkdir /logdir
chown mysql /logdir
systemctl restart mysqld
ls /logdir/plj.*

手动生成新的日志文件几种方法:

1.重启mysql服务
2.执行SQL操作,登陆mysql后执行命令: flush logs;
3.mysqldump --flush-logs
4.mysql -uroot -p123456 -e ‘flush logs‘

查看日志文件内容,查看日志文件记录新数据的范围,并记录偏移量的范围:

mysqlbinlog /logdir/plj.000001

执行binlog日志记录的sql命令恢复数据:

方法一:
mysqlbinlog --start-position=958 --stop-position=1153 /logdir/plj.000001

方法二:
mysqlbinlog --start-datatime="2018/11/21 15:26:31" --stop-datatime="2018/11/21 15:31:16" /logdir/plj.000001

使用完全备份文件恢复数据:

mysql -uroot -p123456 db4 < /root/t2.sql

MySQL基础命令

标签:ldb   表结构   路径   foreign   lint   最小   添加   数值   index   

原文地址:https://www.cnblogs.com/jiang-bokeyuan/p/11703455.html

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