MySQL - CRUD operations

增

That is, a new row is added to the selected table in the database

全部插入

insert into 表名 values(值1,值2 ...);

Insert selected columns

insert into 表名(指定列名1, 指定列名2...) values(值1, 值2...);

删

That is, delete a row from the selected table in the database

delete from 表名;

我们可以用whereKeywords to filter the condition of the column we want to delete

delete from 表名 where 条件;

需要注意的是,在MySQL中,Our logical operator sumJava与CLanguage is different,Some common situations are listed below.

操作符含义

运算符	含义
> ,>=,<,<=	Consistent with normal logic
=	和C语言不同,MySQLIn the judgment of equality, use single equals
<=>	Determine whether both sides arenull,都为null返回true
!=, <>	不等于
between a and b	判断是否在>= a , <= b的范围内
in(a , b, c…)	判断是否为a,b,c中的一个
is null	判断是否为null,是则返回ture
is not null	判断是否为null,是则返回false
like	模糊查询,%表示·多个字符,_表示单个字符
and	相当于&&
or	相当于||
not	相当于～

查

select 查询范围 form 表名;

We can use it in the query scope position*,It means that we want to query all the data

select * form 表名;

同样的,我们也可以用whereto filter our query criteria

select * form 表名 where 筛选条件;

去重

我们可以用distinctkeyword to deduplicate the query results

select distinct 查询范围 from 表名;

排序

我们可以用order by关键字来对查询结果进行排序

升序

select 查询范围 from 表名 order by asc;

降序

select 查询范围 from 表名 order by desc;

别名

We can alias query results

select header expression 别名 from 表名; 

分页

When our query data volume is too large,We can query page by page like a browser
使用关键字limit

select * from 表名 limit Limit the number of displays;

我们用offset进行翻页,The default first page offset is 0

select * from 表命 limit Limit the number of displays offset 偏移量;

改

update 表名 set 表头 = 表达式 where 条件;

需要注意的是,Our data operations are very dangerous,一定要小心谨慎