mysql 杂记

1.字符集与储存引擎

--没有指定引擎与字符集
create table if not exists `goods`(
    `id` int unsigned not null auto_increment  primary key,

    `goodsname` varchar(255) not null 

)engine=innodb default charset=utf8;

1.如果不指定存储引擎，使用的是配置文件的默认值
2.如果不制定表的字符集，使用的是配置文件设置的字符集

    工作中没有权限修改

3.设置指定数据库的字符集
    alter database 数据库名 character set 字符集;
    alter database jn_user chaeacter SET utf8;
4.修改表的字符集
    ALTER TABLE `表名` DEFAULT CHARACTER SET 字符集;
    ALTER TABLE `goods` DEFAULT CHARACTER SET gbk;

使用黑窗口查正确显示内容，请设置 set names gbk;
        这是与操作系统有关

无论如何，在建表时，请设置好字符集与存储引擎，解决不必要的配置

2.查

查询语句，最灵活，最麻烦
--建表    
create table if not exists `goods`(
    `id` int unsigned not null auto_increment ,
    primary key (`id`),
    `name` varchar(255) not null ,
    `price` float(8,2) not null ,
    `image` varchar(255) not null ,
    `color` varchar(32) not null ,
    `size` varchar(32) not null ,
    `evaluate` int unsigned  not null 
)engine=innodb default charset=utf8;

insert into `goods`(`name`,`price`,`image`,`color`,`size`,`evaluate`) values
    ('文胸1',199,'1.jpg','黑色','36e','1'),
    ('文胸2',199,'2.jpg','蓝色','36e','1'),
    ('文胸3',199,'3.jpg','白色','36e','1'),
    ('文胸4',199,'4.jpg','黑色','36e','1'),
    ('文胸5',199,'6.jpg','绿色','36e','1'),
    ('文胸6',199,'21.jpg','黑色','36e','1'),
    ('文胸7',199,'13.jpg','黑色','70A','1'),
    ('文胸8',199,'11.jpg','黑色','36e','1'),
    ('文胸9',199,'14.jpg','黑色','36e','1'),
    ('文胸10',199,'51.jpg','黑色','36e','1'),
    ('文胸11',199,'17.jpg','黑色','71B','1'),
    ('文胸12',199,'19.jpg','黑色','36e','1'),
    ('文胸13',199,'12.jpg','黑色','36e','1'),
    ('文胸14',199,'13.jpg','红色','72C','1'),
    ('文胸15',199,'12.jpg','黑色','36B','1'),
    ('文胸16',199,'16.jpg','黑色','73D','1'),
    ('文胸17',199,'13.jpg','黑色','36e','1'),
    ('文胸18',199,'12.jpg','黑色','36e','1'),
    ('文胸19',199,'1.jpg','黑色','36e','1'),
    ('文胸20',199,'1.jpg','黑色','36e','1'),
    ('文胸21',199,'1.jpg','黑色','36e','1'),
    ('文胸22',199,'1.jpg','黑色','36e','1'),
    ('文胸23',199,'1.jpg','黑色','36e','1'),
    ('文胸24',199,'1.jpg','黑色','36e','1'),
    ('文胸25',199,'1.jpg','黑色','36e','1');


1.查询所有字段，所有数据
    select * from `goods`;
2.查询指定字段，所有数据
    select `id`,`name`,`price` from `goods`;

查询所有数据，会扫描整个数据库。
所以，不要在高峰期使用 查询所有数据。

3.等于    = 
    select * from `goods` where `size` = '70A';
    select * from `goods` where `id` = 16;

4.<=>
    添加测试字段
    alter table `goods` add `click_num` int unsigned;
    --点击量

    -- 不识别 null 
    select * from `goods` where `click_num` = null;
    -- 识别 null 
    select * from `goods` where `click_num` <=> null;

5.查询空格  is null 或 is not null
    -- 点击量为空类型的数据
    select * from `goods` where `click_num` is null;

    -- 点击量不为空的数据
    select * from `goods` where `click_num` is not null;

6.不等于 != 或 <> 没有区别
    select * from `goods` where `id` != 10;
    select * from `goods` where `id` <> 10;

    select * from `goods` where `size` != '36e';

    --都不识别null
    select * from `goods` where `click_num` != null;
    select * from `goods` where `click_num` <> null;

8.  > , >= ,<  , <=
    select * from `goods` where `id` >13; 
    select * from `goods` where `id` >=13;
    select * from `goods` where `id` <13; 
    select * from `goods` where `id` <=13;      
9.between and 数值范围 , not between and
    --id 11到13的数据
    select * from `goods` where `id` between 11 and 13;

    --除了12到14的数据
    select * from `goods` where `id` not between 12 and 14;



10.and 与 ， or 或
    and 满足两条件
    or 只满足一个条件
    update `goods` set `price` = 299 , `image` = '2.jpg' where `id` = 11;
    update `goods` set `price` = 399 , `image` = '3.jpg' where `id` = 12;
    update `goods` set `price` = 499 , `image` = '4.jpg' where `id` = 13;
    update `goods` set `price` = 599 , `image` = '5.jpg' where `id` = 14;
    update `goods` set `price` = 99 , `image` = '6.jpg' where `id` = 15;
    update `goods` set `price` = 9 , `image` = '7.jpg' where `id` = 16;

    update `goods` set `click_num` = 100 where `id` = 11;
    update `goods` set `click_num` = 200 where `id` = 12;
    update `goods` set `click_num` = 300 where `id` = 13;
    update `goods` set `click_num` = 400 where `id` = 14;
    update `goods` set `click_num` = 500 where `id` = 15;
    update `goods` set `click_num` = 600 where `id` = 16;

    --价格小于300，点击量大于400
    select * from `goods` where `price` < 300 and `click_num` > 400;

    --or 或
    select * from `goods` where `price` < 300 or `click_num` > 400;

11.in , not in 范围集合

    select * from `goods` where `id` in(11,13,15);

    --除了范围集合
    select * from `goods` where `size` not in('72C','73D','75B');

12.like 模糊查询
    % 任意长度
        李%
            李开头
        %勇
            勇结尾
        %宝%
            包含宝字的

    _一位长度       

    insert into `goods` values
        (null , '凹凸文胸3',999,'a.jpg','灰白','100B',2,899),
        (null , '凹凸巨大文胸',999,'a.jpg','灰白','100B',2,899),
        (null , '凹凸巨大文胸',999,'a.jpg','灰白','100B',2,899),
        (null , '凹凸曼妮芬大文胸',999,'a.jpg','灰白','100B',2,899);
    insert into `goods` values
        (null , '百度',999,'a.jpg','灰白','100B',2,899),
        (null , '白百合',999,'a.jpg','灰白','100B',2,899),
        (null , '白骨晶',999,'a.jpg','灰白','100B',2,899),
        (null , '白日',999,'a.jpg','灰白','100B',2,899);

    select * from `goods` where `name` like '凹凸%';
    select * from `goods` where `name` like '白%';

    select * from `goods` where `name` like '%胸';
    select * from `goods` where `name` like '%大%';
    select * from `goods` where `name` like '_日';
    select * from `goods` where `name` like '白__';

13.去重查询
    select distinct 字段 from 表名;
    select distinct `image`,`size` from `goods`;

14.排序 order by 
    select * from `goods` order by `id` asc;--顺序
    select * from `goods` order by `id` desc;--倒叙

15.使用表达式
    select `id`,`name`,`price` + 1 from `goods`;

    -- 取原数据再计算

    update `goods` set `price` = `price` + 1 where `id` = 25;

    -- 更新点击量
    update `goods` set `click_num` = `click_num` + 1 where `id` = 24; 

    1. concat() 字符链接
        select `id`,concat(`name`,' 大特卖') from `goods`;
    2.count()总数
        select count(*) from `goods`;--计算表的总数量
    3.计算和
        select sum(`click_num`) from `goods`;
    4.avg() 平均值 
        select avg(`click_num`) from `goods`;
    5.max() 最大 
        select max`click_num`) from `goods`;
    min最小

16.分组查询

    -- 以指定字段分组，并统计每组数量
    select `color`,count(*) from `goods` group by `color`;

    -- 查询 evaluate ，并以 evaluate 进行分组，并计算每组的最大值
    select `evaluate`,max(`price`) from `goods` group by `evaluate`;

    -- 查询 evaluate ，并以 evaluate 进行分组，并计算每组的最大值
    select `evaluate`,max(`price`) from `goods` group by `evaluate`;

17.limit 限制查询结果
    -- 按照默认顺序，显示一条数据
    select * from `goods` limit 1;

    select * from `goods` order by `id` desc limit 1;

    select * from `goods` where `price` <= 599 order by `price` desc limit 3 ;
    order by desc limit 按顺序来
    -- 分页 limit 偏移量,长度;

    -- 获取总数
    select count(*) from `goods`; -- 总数

    -- 假设每页显示 5 条数据 
    -- 求总页码数 ： ceil( 总数 / 每页显示条数 ) = 4 
    -- 偏移量的计算公式：（当前页码 - 1） * 每页显示条数 == 偏移量


    -- 第一页 （1-1）*5 = 0
    select * from goods order by `id` desc limit 0,5;

    --  第2页     (2 - 1) * 5 = 5
    select * from goods order by `id` desc limit 5 ,5;  -- 第2页  

    --  第3页     (3 - 1) * 5 = 10
    select * from goods order by `id` desc limit 10,5;  -- 第3页

    --  第4页     (4 - 1) * 5 = 15
    select * from goods order by `id` desc limit 15,5;  -- 第4页

18.连接查询


--设计用户表
    create table if not exists `shop_user`(
        `id` int unsigned not null auto_increment,
        primary key(`id`),
        `user` varchar(255) not null ,
        unique un_user(`user`),
        `pass` char(32) not null,
        `icon` varchar(255) not null default 'default.jpg',
        `sex` enum('0','1','2') not null default '2',
        `email` varchar(255) not null default '',
        `address` varchar(255) not null default '',
        `age` int unsigned not null default 0,
        `tel` char(11) not null default '',
        `grade` tinyint unsigned not null default 2,
        `status` tinyint unsigned not null default 1,
        `addtime` int unsigned not null
    )engine=innodb default charset=utf8;

    -- 添加测试数据
    insert into `shop_user`(`user`,`pass`,`addtime`) values('admin',md5('123'),unix_timestamp());
    insert into `shop_user`(`user`,`pass`,`addtime`) values('大勇',md5('123'),unix_timestamp());
    insert into `shop_user`(`user`,`pass`,`addtime`) values('jack',md5('123'),unix_timestamp());
    insert into `shop_user`(`user`,`pass`,`addtime`) values('提莫',md5('123'),unix_timestamp());


    --创建收货地址表
    create table if not exists `shop_address`(
        `id` int unsigned not null auto_increment ,
        primary key(`id`),
        `user_id` int unsigned not null ,
        `name` varchar(255) not null ,
        `address` varchar(255) not null ,
        `tel` char(11) not null ,
        `email` varchar(255) not null ,
        `status` tinyint unsigned not null default 0,
        `addtime` int unsigned not null 
    )engine=innodb default charset=utf8;

    insert into `shop_address` values
        (null , 1, '大勇','dongpu大马路','13922130889','[email protected]',1,unix_timestamp()),
        (null , 1, '大勇2b','可能还在读小学','13822130889','[email protected]',1,unix_timestamp()),
        (null , 1, '大勇3','东莞XXXX店','13722130889','[email protected]',1,unix_timestamp()),

        (null , 2, '浪哥','天河白天月','15722130889','[email protected]',1,unix_timestamp()),
        (null , 2, '隔壁老王','天河七天','18722130889','[email protected]',1,unix_timestamp());

    --多表查询
    select * from `shop_user` , `shop_address`;

    内连查询
    SELECT * FROM 表1,表2 WHERE 表1.字段 = 表2.字段;

    select * from `shop_user`,`shop_address` where shop_user.id = shop_address.user_id;

    --查询 用户表的id、用户名、地址，收货地址表的收货人、收货地址
    select shop_user.id , shop_user.user,shop_address.id , shop_address.name , shop_address.address from `shop_user`,`shop_address` where shop_user.id = shop_address.user_id;

    --别名的使用
    select u.id , u.user , a.id , a.name , a.address from `shop_user` as u,`shop_address` as a where u.id = a.user_id;

    --外连接
        以左表为主: 左表的所有数据，都会查询出来，没有与之关联，则填空类型
        select * from 表1 left join 表2 ON 表1.字段 = 表2.字段
        select shop_user.id , shop_user.user , shop_address.user_id , shop_address.name , shop_address.address from shop_user left join shop_address on shop_user.id = shop_address.user_id;


    -- 起别名
        select u.id , u.user , a.user_id , a.name , a.address from shop_user as u left join shop_address as a on u.id = a.user_id;

    -- 以右表为主，右表的所有数据都会查询，并与左表关联

    右连：SELECT * FROM 表1 RIGHT JOIN 表2 ON 表1.字段 = 表2.字段

    select u.id,u.user , a.user_id , a.name , a.address from shop_user as u right join shop_address as a ON u.id = a.user_id;

    -- 子查询
    查询admin用户的所有收货地址
            1.知道 admin 的 id
                select id from shop_user where `user` = 'admin'; 1

            2.拿着 admin 的 id去查询 shop_address 条件就是 id = user_id
                select * from shop_address where `user_id` = 1;



    合体(子查询)
        select * from shop_address where `user_id` = (select id from shop_user where `user` = 'admin');
        select * from shop_address where `user_id` in(select id from shop_user where `user` = 'admin');

    数据的复制
        -- 复制表结构
            create table 新表 like 旧表;
            create table n_address like shop_address;

            -- 复制数据
            insert into 新表 select * from 旧表;
            insert into n_address select * from shop_address;

创建或授权 必须是 root 用户才可以使用授权功能

grant 权限 on 数据库.数据表 to 用户名@登录主机 identified by "密码"

1.用户已经存在，则更新权限
2.用户不存在，添加用户并授权

%           可远程登录
localhost   本地登录 

grant select,update,delete,insert on t4.shop_address to cindy@localhost identified by 'root';

grant select,update,delete,insert on t4.shop_address to cindy@"%" identified by 'root';

all ： select , insert , delete , update 

*.* 所有库.所有表

grant all on *.* to cindy@localhost identified by 'root';

--远程登录
mysql  -h ip -u cindy -proot

--user表在mysql库里
--删除用户
delete from `user` where `user` = 'cindy';

--更新权限
flush privileges;

--更改密码 update 
    update `user` set `password` = password('123') where `user` = 'zhiyong';
-- 更新权限
flush privileges;

-- 超级管理员的密码忘记了

update `user` set `password` = password('123') where `user` = 'root'; 
--重启服务器

数据库备份

--备份一个库
mysqldump -u root -p jn > d:/jn.sql



-- 还原一个库
-- 必须先创建一个库 
mysql -u root -p t6 < d:/jn.sql 

--备份一个表
mysqldump -u root -p 库名 表名 > d:/文件名.sql

--使用source还原数据表
    --必须选库
    use 库;
    source 路径

取别名：

        as
        select name as '姓名' from jn_user;