什么是SQLite
SQLite 是一个小型的、无数据类型的、开源的，可嵌入的关系型数据库，它支持事务操作。
1.数据类型
1.1 SQLite使用动态数据类型，根据存入的值自动进行判断，对于每一个值都属于下面存储类型之一
NULL：空值；
INTEGER：整型
REAL：浮点数类型
TEXT：值为文本字符串
BLOB：存储Blob数据，该类型数据和输入的数据完全相同；
1.2 为了最大化SQLite和数据库引擎之间的数据库兼容，SQLite提出类型亲缘性（Type Affinity）的概念，在表字段声明后，SQLite会根据字段声明的类型选择一种亲缘类型。
2. sql语句(几个重要的参数 表名，字段名，数据类型 约束条件)
2.1 创建表
create table 表名 (字段名称 数据类型 约束 ……)
create table person(_id Integer primary key,name varchar(10),age Integer not null)
2.2 删除表
create table 表名
create table person
2.3 插入数据
insert into 表名 （字段名称1，字段名称2）values (值1，值2);
insert into person(_id,age) values (1,20)
insert into person values (2,”gzc”,20);
2.4 修改数据
update 表名 set 字段=新值 where 修改的条件
update person set name =”gzc” ,age = 23 where _id =1
2.5 删除数据
delete from 表名 where 删除的条件
delete from person where _id = 2
2.6 查询语句
select 字段名 from 表名 where 查询条件 group by 分组的字段 having 筛选的条件 order by 排序的字段
select _id,name from person
select * from person where _id = 1
select * from person where _id <>1
select * from person where _id=1 and age <18
select * from person where age between 10 and 20
select * from person where name like “%陈%”
select * from person where name like “_陈%””_”代表一个字符 “%” 代表多个字符
select * from person where name is null
select * from person where age >20 order by _id
//增
sqlite> create table student(id integer , name varchar(3),age int);//创建一个table
create table student(id integer primary key autoincrement,age int,name varchar(30));
sqlite> .table//显示所有
sqlite> insert into student values(1,”jack”,18); //添加
sqlite> insert into student(stuNo,name)values(3,’tom’);
alter table student add column job Stirng; //增加某一列；
//删
delete from student;//删除所有数据；
delete from student where id = 1;//删除id = 1 的所有数据；
drop table student;
//改
update student set name = job,age = 12 where id = 1;
update student set name = ‘lucy’ where id = 52;
//查
select * from student //查询全部；
sqlite> select name from student; //按照name选择
sqlite> select * from student where stuNo>2;//按照stuNo选择
sqlite> select * from student where stuNo>2 and name = ‘tom’;
sqlite> select * from student where stuNo>2 or name = ‘tom’;
sqlite> select * from student where stuNo in(2,3);//选择某一个区间的值
sqlite> select * from student where stuNo not in(2,3);//选择不再某个区间的值
select * from student order by stuNo desc;//降序
select * from student order by stuNo asc;//升序
聚合函数
select count(*) from student; //查询所有记录数；
select count(age) from student; //查询某个字段的集合；
select sum(age) from student;//求和
select min(stuNo) from student;//求最小值
select max(stuNo) from student;//求最大值
select avg(age) from student;//求平均值
select * from student where name like’j%’;//以j开头;
select * from student where name like’%k’;//以k结尾;
select * from student where name like’%o%’;//中间含有o;
select * from student where id in(5,7);
select * from student where id>=5 and id<=7;
select * from student where id between 5 and 7;
