MySQl操作整理01

MySQl操作整理01

• 连接数据库：

mysql -u [useename] -p
mysql -u [username] -h [host] -p

• 用户管理：

create user 'spring'@'192.168.1.1' identified by '123';
create user 'spring'@'192.168.1.%' identified by '123';
create user 'spring'@'%' identified by '123';

drop user 'spring'@'%';
rename user 'spring'@'%' to 'new_spring'@'%';
set password for 'spring'@'%' = password('ab123');

• 权限管理：

grant select,insert,update on db1.t1 to 'spring'@'%';
grant all privileges on db1.t1 to 'spring'@'%';
revoke all privileges on db1.t1 from 'spring'@'%';

• 数据库操作：

create database db1 default charset=utf8;
create database db1 default charset utf8;
drop database db1;

show databases;

–

对数据表的操作：

show tables;

create table t1(
    列名 类型 null,
    列名 类型 not null,
    列名 类型 not null auto_increment primary key,
    id int,
    name char(10)
)engine=innodb default charset=utf8;
    # innodb  支持事物，原子性操作 ****
    # myisam 
    not null：是否为空
    auto_increment  表示自增

    primary key  主键表示约束(不能重复且不能为空)；加速查找；加速查找
    一个表只能有一个主键
    主键可以由多列组成
create table t2(
    nid int(11) not null auto_increment,
    pid int(11) not null,
    num int(11),
    primary key(nid,pid)    
)engine=innodb default charset=utf8;


create table t3(
    id int auto_increment primary key,
    name char(10),
    id1 int,
    id2 int,
    constraint fk_t3_t2 foreign key(id1,id2) reference t2(nid,pid)
)engine=innodb default charset=utf8;


外键:
    create table department(
        id bigint auto_increment primary key,
        title char(15)
    )engine=innodb default charset=utf8;

    create table userinfo(
        uid bigint auto_incremant peimary,
        name varchar(32),
        department_id int,
        constraint fk_user_depar foreign key (department_id) reference color(id)
    )engine=innodb default charset=utf8;




清空表:
    delete from t1;
    truncate table t1; #清除auto_increment自增
删除表:
    drop table t1;

修改表:
    添加列: alter table 表名 add 列名 类型;
    删除列: alter table 表名 drop column  列名；
    修改列: 
           alter table 表名 modify column 列名 类型; -- 类型
           alter table 表名 change 原列名 新列名 类型；-- 列名,类型    
    添加主键:
           alter table 表名 add primary key(列名)
    删除主键:
           alter table 表名 drop primary key;
           alter table 表名 modify 列名 int, drop primary key;
    添加外键:
           alter table 从表 add constraint 外键名(形如:FK_从表_主表) foreign key 从表(外键字段) references 主键(主键字段)；
    删除外键:
           alter table 表名 drop foreign key 外键名称 
    修改默认值：
           alter table 表名 auto_increment=20;       
查看表结构:
    desc t1;
查看创建表信息:
    show create table t1;

数据类型：

        数据类型:
            数字、字符串、时间类型
            数字:
                tinyint
                int
                bigint

                float
                double
                decimal
            字符串:
                char(10)    速度快 (10)示10个字符
                varchar(10) 节省空间
                PS:创建数据表长列往前放
            时间类型
                datetime
            enum
            set
            create table t1(
                id int signed auto_increment primary key,
                num decimal(10,5),
                name char(10)
            )engine=innodb default charset=utf8;
 #拿tinyint字段来举例，unsigned后，字段的取值范围是0~255，而signed的范围是-128~127

对数据行进行操作:

    insert into t1(name,age) values('autumn',18),('spring',19);
    insert into t1(name,age) select name,age from tb2;

    delete from t1 where id >6;
    delete from t1 where id != 6;
    truncate table t1; #清除auto_increment自增

    update t1 set name='root' where id=5;
    update t1 set name ='autumn' where id=6 and age=18;

    select * from t1;
    select id,name from t1;

查询操作

• 临时表：

    select num,course_id from (select num,course_id from score where num >60) as B;

    select * from t1;
    select * from t1 where id=1;
    select * from t1 where id!=2;
    select * from t1 where id >2;
    select * from t1 where id >=2 and name='spring';
    select name,age from t1;
    select * from t1 where id in (1,2,3);
    select * from t1 where id not in (1,2,3);
    select * from t1 where id in (select id from t2);
    select * from t1 where id between 5 and 12;包括2和12

    通配符:
          select * from t1 where name like "a%"
          select * from t1 where name like "a_"
    分页:
        select * from t1 limit 10;
        select * from t1 limit 0,10;
        select * from t1 limit 10,10;

        select * from t1 limit 2 offset 4; 从第5个开始往后2个  

    排序:
        select * from t1 order by id desc;从大到小
        select * from t1 order by id asc; 从小到大
        select * from t2 order by id desc, age asc;
        distinct:
        select DISTINCT student_id from score where num < 60

        取最后5条数据
        select * from t1 order by id desc limit 5;

    分组:
        select  count(1),max(id),part_id from userinfo group by part_id;

        count()
        max()
        min()
        sum()
        avg()
        *******如果对聚合函数进行二次筛选时，必须使用having******
        select count(1),max(id),part_id from userinfo group by part_id having count(id) > 1;
        select count(id),part_id from userinfo where id >0 group by part_id having count(id) > 1;

    连表操作:
        select * from userinfo,department;笛卡尔基
        select * from userinfo,department where userinfo.uid =department.id
        select * from userinfo left join department on userinf.uid = department.id(在之前版本的myqsl中 这两种方式是有性能差别，但是在现在版本的mysql中性能是一样的，推荐用 left join 的方法)
        select * from userinfo right join department on userinfo.uid = department.id
        left:左边表全显示，right:右边全显示

        select * from userinfo innder join department on userinfo.uid = department.id
        将出现null的一行隐藏 

        select * from 
            department5 
            left join userinfo5 on userinfo5.part_id =department5.id
            left join userinfo6 on userinfo5.part_id =department5.id

        select 
            score.sid,
            student.sid 
            from 
        score
            left join student on score.student_id = student.sid
            left join course on score.course_id = course.cid
            left join class on student.class_id = class.cid
            left join teacher on course.teacher_id=teacher.tid

        select count(id) from userinfo;