236 lines
5.5 KiB
Markdown
236 lines
5.5 KiB
Markdown
## 实机操作
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进入名为 sys 数据库
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```mysql
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use sys;
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```
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创建表 person
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```mysql
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create table person(
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id int not null primary key auto_increment,
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name char(40) not null default '',
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age int not null default 20,
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info char(5) null
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);
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```
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查看数据
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```mysql
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desc person;
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```
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查看表内数据
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```mysql
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select * from person;
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```
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插入数据
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```mysql
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insert into person (id,name,age,info)
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values(1,'Green',21,'lar');
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```
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查看数据
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插入数据
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```mysql
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insert into person (id,age,name,info) values(2,22,'su','do');
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```
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查看数据
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插入数据
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```mysql
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insert into person values(3,'wang',23,'ji');
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```
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查看数据
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插入数据
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```mysql
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insert into person (age,name,info) values(32,'xu','deo');
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```
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查看数据
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插入指定字段
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```mysql
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insert into person (age,name,info) values(32,'xu','deo');
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insert into person (name,age)values('wan',23);
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insert into person (name)values('win');
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```
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插入多条数据
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```mysql
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insert into person (age,name,info)
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values(26,'xi','dreo'),
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(22,'ju','do'),
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(39,'vheng','dxu');
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```
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创建新表
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```mysql
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create table person2(
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id int not null primary key auto_increment,
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name char(40) not null default '',
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age int not null default 20,
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info2 char(5) null
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);
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```
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将查询结果插入到表中
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```mysql
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insert into person2 (id,name,age,info2)
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select * from person;
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```
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、
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更新数据
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```mysql
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update person set age=15,name='liming' where id=9;
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```
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查询语句限制
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```mysql
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select * from person where id=9;
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*是指泛指
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select name from person where id=9;
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```
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查询年龄在19到25之间的人
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```mysql
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select * from person where age between 19 and 25;
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```
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删除表中 id 为9的人
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```mysql
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delete from person where id=9;
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```
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删除所有表中数据
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```mysql
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delete from person;
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```
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## 一、插入数据
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### 1.为表的所有字段插入数据
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```mysql
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insert into 表名 (字段名,字段名,字段名)
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values(对应字段的值,对应字段的值,对应字段的值);
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```
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备注：允许字段名顺序与建表时顺序不同，不需要按照表定义的顺序插入，只要保证值的顺序和前面字段名的顺序相同即可。
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例：insert into person (id,age,name,info) values(2,22,'su','do');
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备注2：使用insert语句插入数据时，允许将字段名省略，此时注意，值列类表需要为表中的每一个字段赋值，并且值的顺序必须与建表时各个字段的顺序相同。
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例：insert into person (id,age,name,info) values(2,22,'su','do');
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### 2.为表指定字段插入数据
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为表的指定字段插入数据，就是在 insert 语句中指向部分字段插入值，而其他字段的值为表定义时的默认值。
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例：insert into person (age,name,info) values(32,'xu','deo');
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insert into person (name,age)values('wan',23);
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insert into person (name)values('win');
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备注：要保证每个插入值的类型和对应字段的数据类型保持一致，否则报错
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### 3.同时插入多条数据
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insert into 表名 (各个字段名) values(第一条记录的值列表), (第二条记录的值列表), (第三条记录的值列表)
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例：
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```mysql
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insert into person (age,name,info)
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values(26,'xi','dreo'),
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(22,'ju','do'),
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(39,'vheng','dxu');
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```
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### 4.将查询结果插入到表中
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语法：insert into 新表名(字段名)查询语句;**此处没有values**
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注意：两个表的数据类型必须一致，字段个数也要一致。
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insert into person2 (id,name,age,info2)select * from person;
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## 二、更新数据
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update 表名 set 需要更新字段名1=值,需要更新的字段名2=值 where 条件;
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补充：select 字段名 from 表名 where 条件;
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select * from person where age between 19 and 25;
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## 三、删除数据（删除操作是不可逆的删除时一点要小心）
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1.有选择删除
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语法：delete from 表名 where 限定条件;
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例：delete from person where id=9;
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2.删除表中所有数据
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语法：delete from 表名;
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