MySQL5.7 mysql.user表没有password字段改 authentication_string；

一. 创建用户:

命令:

CREATE USER 'username'@'host' IDENTIFIED BY 'password';

例子:

CREATE USER 'dog'@'localhost' IDENTIFIED BY '123456';

CREATE USER 'dog2'@'localhost' IDENTIFIED BY '';

PS：username - 你将创建的用户名,

host - 指定该用户在哪个主机上可以登陆，此处的"localhost"，是指该用户只能在本地登录，不能在另外一台机器上远程登录，如果想远程登录的话，将"localhost"改为"%"，表示在任何一台电脑上都可以登录;也可以指定某台机器可以远程登录;

password - 该用户的登陆密码,密码可以为空,如果为空则该用户可以不需要密码登陆服务器。

二.授权:

命令:

GRANT privileges ON databasename.tablename TO 'username'@'host'

PS:

privileges - 用户的操作权限,如SELECT , INSERT , UPDATE 等(详细列表见该文最后面).如果要授予所的权限则使用ALL.;

databasename - 数据库名,tablename-表名,如果要授予该用户对所有数据库和表的相应操作权限则可用表示, 如.*.

例子:

GRANT SELECT, INSERT ON mq.* TO 'dog'@'localhost';

三.创建用户同时授权

mysql> grant all privileges on mq.* to test@localhost identified by '1234';Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> flush privileges;Query OK, 0 rows affected (0.01 sec)

PS:必须执行:

**flush privileges; **

**否则登录时提示：ERROR 1045 (28000): Access denied for user 'user'@'localhost' (using password: YES ) **

四.设置与更改用户密码

命令:SET PASSWORD FOR 'username'@'host' = PASSWORD('newpassword');

例子: SET PASSWORD FOR 'dog2'@'localhost' = PASSWORD("dog");

五.撤销用户权限

命令: REVOKE privilege ON databasename.tablename FROM 'username'@'host';

说明: privilege, databasename, tablename - 同授权部分.

例子:

REVOKE SELECT ON mq.* FROM 'dog2'@'localhost';

PS:

假如你在给用户'dog'@'localhost''授权的时候是这样的(或类似的):GRANT SELECT ON test.user TO 'dog'@'localhost', 则在使用REVOKE SELECT ON . FROM 'dog'@'localhost';命令并不能撤销该用户对test数据库中user表的SELECT 操作.相反,如果授权使用的是GRANT SELECT ON . TO 'dog'@'localhost';则REVOKE SELECT ON test.user FROM 'dog'@'localhost';命令也不能撤销该用户对test数据库中user表的Select 权限.

具体信息可以用命令SHOW GRANTS FOR 'dog'@'localhost'; 查看.

六.删除用户

命令: DROP USER 'username'@'host';

七.查看用户的授权

mysql> show grants for dog@localhost;+---------------------------------------------+| Grants for dog@localhost |+---------------------------------------------+| GRANT USAGE ON *.* TO 'dog'@'localhost' || GRANT INSERT ON `mq`.* TO 'dog'@'localhost' |+---------------------------------------------+2 rows in set (0.00 sec)

PS:

GRANT USAGE:mysql usage权限就是空权限，默认create user的权限，只能连库，啥也不能干**

人生如果错了方向，停止就是进步

最近想做一个即时通讯的Android demo，但是一直不知道如何处理用户和好友之间的表关系。在网上找了好久也没找到合适的。我本人很少接触数据库，对数据库语句比较差。

但是这只是自己demo，只能自己写。

创建数据库

好了，不多逼逼，现在开始创建一个数据库吧。

create database my_chat;

这一步相信大家都很明白，就是创建了一个my_chat的数据库

创建表

选择数据库

use my_chat;

创建用户表

create tableuserTable

(

userIdint auto_increment primary key, --用户ID自增

password varchar(100), --密码

userName varchar(100) unique, --用户名

birthYear smallint, --出生年

birthMonth smallint, --出生月

birthDay smallint, --出生日

gender smallint, --0 为女性, 1 为男

avatarId int, --头像Id

isOnline int, --0 为离线, 1 在线

signupTime varchar(100), --XXXX-XX-XX-XX-XX (year-month-day-hour-minute)注册日期

hometown varchar(100), --家乡

location varchar(100) --现居住地

);

添加用户表信息

insert intouserTable(password,userName,birthYear,birthMonth,birthDay,gender,avatarId,isOnline,signupTime,hometown,location)values("123456","test1",1997,09,23,1,0,1,"2020-09-23","广西/百色","广东珠海");insert intouserTable(password,userName,birthYear,birthMonth,birthDay,gender,avatarId,isOnline,signupTime,hometown,location)values("123456","test2",1998,03,26,0,1,1,"2020-09-23","广西/百色","广东珠海");

创建好友表

create tablefriendListTable

(

masterIdint, --此好友列表所属用户的id

friendId int, --好友Id

friendName varchar(100), --好友姓名

friendBirthYear smallint, --好友出生年

friendBirthMonth smallint, --好友出生月

friendBirthDay smallint, --好友出生日

friendGender smallint, --好友友性别

friendAvatarId int, --好友头像

friendIsOnline int, --好友在线状态

friendSignupTime varchar(100), --好友注册日期

friendHometown varchar(100), --好友家乡

friendLocation varchar(100), --好友现居住地

foreign key(masterId) references userTable(userId) on delete cascade --当用户信息修改或删除，该表同步修改

);

添加好友数据

insert intofriendListTable(masterId,friendId,friendName,friendBirthYear,friendBirthMonth,friendBirthDay,friendGender,friendAvatarId,friendIsOnline,friendSignupTime,friendHometown,friendLocation)values(1,2,"test2",1998,03,26,0,1,1,"2020-09-23","广西/百色","广东珠海");insert intofriendListTable(masterId,friendId,friendName,friendBirthYear,friendBirthMonth,friendBirthDay,friendGender,friendAvatarId,friendIsOnline,friendSignupTime,friendHometown,friendLocation)values(2,1,"test1",1997,09,23,0,0,1,"2020-09-23","广西/百色","广东珠海");

获取所有好友

select * from friendListTable where masterId=2;

获取所有在线好友

select * from friendListTable where masterId=2 and friendIsOnline=1;

获取所有离线好友

select * from friendListTable where masterId=? and friendIsOnline=0;

创建消息表

create tableunSendMsgs

(

senderIdint,

receiverIdint,

msgtext,

_datetime datetime,

typeint)

添加消息数据

insert into unSendMsgs (senderId,receiverId,msg,_datetime,type) values(1,2,"这是n一条测试消息",now(),1);insert into unSendMsgs (senderId,receiverId,msg,_datetime,type) values(2,1,"收到",now(),0);insert into unSendMsgs (senderId,receiverId,msg,_datetime,type) values(1,3,"四号是个大撒比",now(),0);insert into unSendMsgs (senderId,receiverId,msg,_datetime,type) values(3,1,"三号明白",now(),1);insert into unSendMsgs (senderId,receiverId,msg,_datetime,type) values(1,3,"over over",now(),0);

查询一号和三号互相发送的消息

select * from unSendMsgs where senderId=1 and receiverId=3 or senderId=3 and receiverId=1 order by _datetime asc;

结果如下

+----------+------------+-----------------------+---------------------+------+

| senderId | receiverId | msg | _datetime | type |

+----------+------------+-----------------------+---------------------+------+

| 1 | 3 | 四号是个大撒比 | 2020-09-20 12:01:14 | 0 |

| 3 | 1 | 三号明白 | 2020-09-20 12:01:36 | 1 |

| 1 | 3 | over over | 2020-09-20 12:01:51 | 0 |

+----------+------------+-----------------------+---------------------+------+

好了，关于用户表和好友表哦以及消息表的关系就如上，日后可能会继续更新，从0搭建即时通讯demo，喜欢的可以点个赞