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‎database/code/JDBC/.idea/misc.xml‎

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‎database/code/JDBC/.idea/modules.xml‎

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‎database/code/JDBC/.idea/workspace.xml‎

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‎database/code/JDBC/JDBC.iml‎

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<?xml version="1.0" encoding="UTF-8"?>
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<module type="JAVA_MODULE" version="4">
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<component name="NewModuleRootManager" inherit-compiler-output="true">
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<exclude-output />
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<content url="file://$MODULE_DIR$">
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<sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
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</content>
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<orderEntry type="inheritedJdk" />
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<orderEntry type="sourceFolder" forTests="false" />
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</component>
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</module>

‎database/code/建表操作.sql‎

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/*
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CREATE TABLE [schema.]table
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(column datatype [DEFAULT expr] , …
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);
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*/
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--设计要求：建立一张用来存储学生信息的表，表中的字段包含了学生的学号、姓名、年龄、入学日期、年级、班级、email等信息，
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--并且为grade指定了默认值为1，如果在插入数据时不指定grade得值，就代表是一年级的学生
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create table student
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(
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stu_id number(10),
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name varchar2(20),
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age number(3),
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hiredate date,
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grade varchar2(10) default 1,
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classes varchar2(10),
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email varchar2(50)
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);
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insert into student values(20191109,'zhangsan',22,to_date('2019-11-09','YYYY-MM-DD'),'2','1','[email protected]');
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insert into student(stu_id,name,age,hiredate,classes,email) values(20191109,'zhangsan',22,to_date('2019-11-09','YYYY-MM-DD'),'1','[email protected]');
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select * from student;
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--正规的表结构设计需要使用第三方工具 powerdesigner
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--再添加表的列的时候，不能允许设置成not null
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alter table student add address varchar2(100);
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alter table student drop column address;
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alter table student modify(email varchar2(100));
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--重新命名表
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rename student to stu;
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--删除表
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/*
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在删除表的时候，经常会遇到多个表关联的情况，多个表关联的时候不能随意删除，需要使用级联删除
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cascade:如果A,B,A中的某一个字段跟B表中的某一个字段做关联，那么再删除表A的时候，需要先将表B删除
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set null:再删除的时候，把表的关联字段设置成空
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*/
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drop table stu;
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--创建表的时候可以给表中的数据添加数据校验规则，这些规则称之为约束
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/*
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约束分为五大类
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not null: 非空约束，插入数据的时候某些列不允许为空
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unique key:唯一键约束，可以限定某一个列的值是唯一的，唯一键的列一般被用作索引列。
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primary key:主键：非空且唯一，任何一张表一般情况下最好有主键，用来唯一的标识一行记录，
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foreign key:外键，当多个表之间有关联关系（一个表的某个列的值依赖与另一张表的某个值）的时候，需要使用外键
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check约束:可以根据用户自己的需求去限定某些列的值
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*/
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--个人建议：再创建表的时候直接将各个表的约束条件添加好，如果包含外键约束的话，最好先把外键关联表的数据优先插入
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insert into emp(empno,ename,deptno) values(9999,'hehe',50);
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create table student
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(
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stu_id number(10) primary key,
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name varchar2(20) not null,
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age number(3) check(age>0 and age<126),
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hiredate date,
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grade varchar2(10) default 1,
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classes varchar2(10),
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email varchar2(50) unique,
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deptno number(2)
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);
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insert into student(stu_id,name,age,hiredate,classes,email,deptno) values(20191109,'zhansgan',111,to_date('2019-11-09','YYYY-MM-DD'),'1','[email protected]',10);
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alter table student add constraint fk_0001 foreign key(deptno) references dept(deptno);

‎database/code/建表操作.~sql‎

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/*
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CREATE TABLE [schema.]table
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(column datatype [DEFAULT expr] , ��
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);
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*/
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--���Ҫ�󣺽���һ�������洢ѧ����Ϣ�ı������е��ֶΰ�����ѧ����ѧ�š����������䡢��ѧ���ڡ��꼶���༶��email����Ϣ��
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--����Ϊgradeָ����Ĭ��ֵΪ1������ڲ�������ʱ��ָ��grade��ֵ���ʹ�����һ�꼶��ѧ��
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create table student
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(
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stu_id number(10),
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name varchar2(20),
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age number(3),
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hiredate date,
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grade varchar2(10) default 1,
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classes varchar2(10),
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email varchar2(50)
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);
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insert into student values(20191109,'zhangsan',22,to_date('2019-11-09','YYYY-MM-DD'),'2','1','[email protected]');
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insert into student(stu_id,name,age,hiredate,classes,email) values(20191109,'zhangsan',22,to_date('2019-11-09','YYYY-MM-DD'),'1','[email protected]');
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select * from student;
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--����ı��ṹ�����Ҫʹ�õ��������� powerdesigner
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--�����ӱ����е�ʱ�򣬲����������ó�not null
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alter table student add address varchar2(100);
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alter table student drop column address;
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alter table student modify(email varchar2(100));
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--����������
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rename student to stu;
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--ɾ����
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/*
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��ɾ������ʱ�򣬾������������������������������������ʱ��������ɾ������Ҫʹ�ü���ɾ��
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cascade:���A,B,A�е�ijһ���ֶθ�B���е�ijһ���ֶ�����������ô��ɾ����A��ʱ����Ҫ�Ƚ���Bɾ��
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set null:��ɾ����ʱ�򣬰ѱ��Ĺ����ֶ����óɿ�
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*/
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drop table stu;
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--��������ʱ����Ը����е�������������У�������Щ�����֮ΪԼ��
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/*
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Լ����Ϊ�����
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not null: �ǿ�Լ�����������ݵ�ʱ��ijЩ�в�����Ϊ��
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unique key:Ψһ��Լ���������޶�ijһ���е�ֵ��Ψһ�ģ�Ψһ������һ�㱻���������С�
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primary key:�������ǿ���Ψһ���κ�һ�ű�һ����������������������Ψһ�ı�ʶһ�м�¼��
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foreign key:������������֮���й�����ϵ��һ������ij���е�ֵ��������һ�ű���ij��ֵ����ʱ����Ҫʹ�����
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checkԼ��:���Ը����û��Լ�������ȥ�޶�ijЩ�е�ֵ
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*/
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--���˽��飺�ٴ�������ʱ��ֱ�ӽ���������Լ���������Ӻã�����������Լ���Ļ�������Ȱ�������������������Ȳ���
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insert into emp(empno,ename,deptno) values(9999,'hehe',50);
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create table student
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(
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stu_id number(10) primary key,
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name varchar2(20) not null,
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age number(3) check(age>0 and age<126),
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hiredate date,
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grade varchar2(10) default 1,
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classes varchar2(10),
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email varchar2(50) unique,
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deptno number(2)
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);
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insert into student(stu_id,name,age,hiredate,classes,email,deptno) values(20191109,'zhansgan',111,to_date('2019-11-09','YYYY-MM-DD'),'1','[email protected]',10);
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alter table student add constraint fk_0001 foreign key(deptno) references dept(deptno);

‎javase/note/jdk api 1.8_google.chw‎

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