SQL数据库的表table操作方法：查询+插入+删除+增加+修改+替换+排序+运算

================表操作=====================

//创建表

create table
if not exists t_class(class_id
integer primary
key autoincrement,class_name
varchar,person_count integer
default 0)

//删除表

drop table if exists t_person

=================数据操作===================

//插入数据

insert into t_class(class_name,person_count)
values ('class1',10)

//删除所有

delete from t_class

//删除部分

delete from t_class
where class_id=5

//改

update t_class set class_name='newclass'

//指定位置改

update t_class set class_name='oldclass'
where class_id=2

update t_class set class_name='oldclass',person_count='20'
where class_id=2

//查  and —— or —— between…and…

select *
from t_class where class_id=2

//查指定数据

select class_id,person_count
from t_class where class_name='oldclass'

select class_id,person_count
from t_class where class_id=3
and person_count=10

select class_id,person_count
from t_class where class_id=3
or class_id=5 

//查某一范围内

select class_id,person_count
from t_class where class_id
between 3 and 5

//查指定位置

select class_id,person_count
from t_class where class_id
in(3,5)

//不在里面的

select class_id,person_count
from t_class where class_id
not in(3,5)

//查询old开头的

select class_id,person_count
from t_class where class_name
like 'old%'

/以333结尾的

select class_id,person_count
from t_class where class_name
like '%333'

//含有class的

select class_id,person_count
from t_class where class_name
like '%class%'

//获取表的数据总数

select count(*)
from t_class

//获取最值

select min(person_count)
from t_class

select max(person_count)
from t_class

//平均值

select avg(person_count)
from t_class

//和

select sum(person_count)
from t_class

//绝对值

select abs(person_count)
from t_class

//四舍五入

select round(person_count)
from t_class

//去除前后空格

select trim(person_count)
from t_class

//加入显示时的别名—name

select trim(class_name)  name
from t_class

//替换，把c全都用o替换

select replace(class_name,'c','o')
from t_class

//长度—空格也算

select length(class_name)
from t_class

//日期函数

select date()
from t_class

select datetime()
from t_class

//查询新建的里面class_name为空的

select *
from t_class where class_name
is null

//排序—倒序，不写desc默认为正序asc

select * from t_class order by(person_count) desc