MySQL基礎之數據管理【1】

添加記錄

insert [into] tbl_name[(col_name,...)] {value|values}(values...);
--不指定字段名稱時需要按照建表時的字段順序給每一個字段賦值
--插入多條數據用逗號隔開
insert tbl_name value(values...);
insert tbl_name set 字段名稱=值,...;
insert tbl_name[(字段名稱...)] select 字段名稱,... from tbl_name [where 條件];

測試

create database if not exists king default character set 'utf8';
use king;
create table user(
	id int unsigned auto_increment key comment '編號',
	username varchar(20) not null unique comment '用戶名',
	age tinyint unsigned default 18 comment '年齡',
	email varchar(50) not null default '[email protected]' comment '郵箱'
)engine=innodb charset=utf8;
insert user value(1,'king',24,'[email protected]');
insert user value(null,'queen',20,'[email protected]');
insert user(id,username) value(3,'wang');

create table if not exists user2(
	name varchar(20) not null default 'aafd'
)engine=innodb charset=utf8;
insert user2 value('aaa'),
('bbb'),
('ccc');

修改記錄

update tbl_name set 字段名稱=值,字段名稱=值,... [where 條件];
--如果不添加條件，整個表中的記錄都會被更新

測試

update user set age=29 where id=1;
update user set username='黎明',age=1,email='[email protected]' where id=3;
update user set age=age+10;
update user set age=age-5,email=default where id<=5;

刪除記錄

delete from tbl_name [where 條件]
--如果不添加條件，表中所有記錄都會被刪除

測試

delete from user where username='king';
delete from user where age>=23;
delete from user; --刪除表中所有記錄
alter table user auto_increment=1; --將auto_increment重置爲1
truncate [table] tbl_name; --徹底將表清空

查詢記錄 select語句的基本形式

select select_expr,... from tbl_name [where 條件] 
[group by {col_name|position} having 二次篩選] 
[order by {col_name|position|expr} [asc|desc]]
[limit 限制結果集的顯示條數];

select * from tbl_name; --查詢表中所有記錄  *所有字段   
select 字段名稱,... from tbl_name --指定字段的信息
select 字段名稱 [as] 別名名稱,... from db_name.tbl_name; --給字段起別名
select 字段名稱,... from tbl_name [as] 別名; --給數據表起別名
select tbl_name.col_name,... from tbl_name; --表名.字段名

測試

create table user(
	id int unsigned auto_increment key comment '編號',
	username varchar(20) not null unique comment '姓名',
	age tinyint unsigned not null default 18 comment '年齡',
	sex enum('男','女','保密') not null default '保密' comment '性別',
	addr varchar(20) not null default '北京',
	married tinyint(1) not null default 0 comment '0代表未婚，1代表已婚',
	salary float(8,2) not null default 0 comment '薪水'
)engine=innodb charset=utf8;

insert user values(1,'king',23,'男','上海',1,50000);
insert user(username,age,sex,addr,married,salary) values('queen',27,'女','上海',0,25000);
insert user set username='imooc',age=31,sex='女',addr='北京',salary=40000;
insert user values(null,'張三',38,'男','上海',0,15000),
(null,'張子楓',38,'男','上海',0,15000),
(null,'子怡',25,'女','北京',0,85000),
(null,'王菲',62,'女','廣州',0,95000),
(null,'劉德華',14,'男','南京',0,115000),
(null,'吳亦凡',35,'男','上海',0,75000),
(null,'張阿文',14,'男','西安',0,65000),
(null,'經過歷',25,'男','湖南',0,15000);

select * from user;
select username,addr,age from user;
select * from king.user; --不用打開數據庫就可以查詢指定的數據表
select id as 'id',username as '姓名' from user;
select id,username from user as u;
select user.id,user.username from user;