数据库增删改查最简单练习

   create table people

(
  Code Varchar(50) primary key,
  Name Varchar (30) not null,
  Time date,
  Age int,
  Nation varchar(50) references Nation2(Code)

 );
 create table Nation2

(
 Code varchar(50)  primary key,
 Name varchar(50) not null

)

create table Race
(
  Code varchar(50)  primary key,#注意不能设为自增长因为自增长必须为整形，否则报错
  Name varchar (50)

)
 添加数据：
 insert into Nation2 values('001','汉族');

 insert into Nation2 values ('002','回族');

 insert into Nation2 values( '003','苗族');
  
 insert into Nation2 values('004','壮族');

 insert into Nation2 (Code) values('005');
 
 insert into Nation2 (Name)values('蒙古族');
 insert into Nation2 (Code) values('006');#多次试验发现Code带主键的可以多次单个添加code但name 只能第一次添加一个，再添加就报错。或者删了这个在添加也报错
 
 delete from Nation2 where  Code=003;#删除 单个数据
  delete from Race #删除整个数据
  
  select*from people#查询people所有数据
  select*from Nation2 where Code=4 #根据条件查询

 drop table Nation2 #删除整张表
 
 update Nation2 set Name='维吾尔族'where code=003;#修改某个数据

 update people set Name='李四',Time='2000-06-03',Age='16',Nation='回族' where Code=001;# 修改时一定注意最后一个不能加逗号