1. INSERT用于向数据库的表中插入1条记录
insert into 表名 (字段1，字段2,...) values (数据1，数据2，数据3...)
示例
-- 如果表存在，就删除
drop table if exists classes;
show tables;
create table classes (id BIGINT not null auto_increment,
name varchar(10) not null,PRIMARY KEY(id)) default charset=utf8;
select * from classes;
-- 插入全部记录时，省略字段
insert into classes VALUES(1,"一班");
-- 掺入指定的字段
insert into classes (name) VALUES ("二班");
-- 插入多条数据
insert into classes (name,id) values ("三班",3),("四班",4);
select * from classes;
Insert语句总结：
- 可以向指定表插入一条记录
- 语法：insert into 表名 (字段1，字段2,...) values (数据1，数据2，数据3...)
select用于查询表的记录
语法：select 列1，列2，列3，... from 表名 where ... ;
show tables;
create table students (
id BIGINT not null auto_increment,
class_id INT ,
name VARCHAR(10) not null,
gender char(1),
PRIMARY KEY(id)) default charset=utf8;
INSERT into students (class_id,name,gender)VALUES
(1,"小明","M"),
(1,"小红","F"),
(1,"小军","M"),
(2,"小白","F"),
(2,"小兵","M"),
(3,"小王","M"),
(3,"小丽","F");
select * from students;
-- where条件
select * from student where id = 2;
select * from student where id > 3;
select * from student where class_id > 3;
select * from student where gender = 'M';
-- and
select * from student where id > 3;
-- 筛选特定的列
select id,name from students;
-- 聚合查询
-- 获取记录数量
select count(*) from students;
--
select count(*) from students group by class_id;
select class_id,count(*) number from students group by class_id;
-- 多表查询
-- 查询的结果是一个4*7=28条的记录，即2个表的乘积，没什么用
select * from classes,students;
-- 通常使用inner join来进行联合查询
select * from classes inner join students on classes.id = students.class_id;
-- 指定别名来更好的返回结果
select c.id,c.name class_name,s.name student_name,s.gender from classes c inner join students s on c.id = s.class_id;
select查询总结：
- 可以指定查询的列
- 可以通过where条件筛选符合条件的记录
- 可以使用聚合查询
- 可以多表联合查询
- 查询结果仍然是一个关系表
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