#获取两个表中字段匹配关系的记录
select a.user_code, a.user_name, b.user_code, b.user_name from app_users a inner join app_users_bak b on a.user_code = b.user_code
#获取左表所有记录，即使右表没有对应匹配的记录
select a.user_code, a.user_name, b.user_code, b.user_name from app_users
insert into app_users_bak(user_code, user_name) select user_code, user_name from app_users;
select case when user_code = ‘9001’ then ‘j’ when user_code = ‘9002’ then ‘z’ else ‘h’ end from app_users;
select * from cms_users limit 0, 3
insert into cms_users(user_code, user_name) values(‘9006’, ‘nono’)
delete from cms_users where user_id = 1
update cms_users set user_name = ‘ko’ where user_id = 2
truncate table cms_users
select * from app
#union all 含重复数据
select * from app_users
union all
select * from app_users_bak
order by user_id
#union 操作符已经删除了重复数据
select * from app_users
union
select * from app_users_bak
order by user_id
1、启动
net start mysql
2、停止
net stop mysql
3、登录
mysql -h 127.0.0.1 -u root -p
4、查看数据库
show databases;
5、使用数据库
use test;
6、查看表列表
show tables;
7、查看表结构
desc app_users
8、断开连接
quit
package com.ssm.cts.test;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.Map;
import java.util.Stack;
import java.util.Vector;
public class ClassTest {
package com.ssm.cts.test;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Stack;
import java.util.Vector;
public class ClassTest {
// 测试
public static void main(String[] args) {
Hashtable<String, String&g
package com.ssm.cts.test;
import java.util.Enumeration;
import java.util.Stack;
import java.util.Vector;
public class ClassTest {
// 测试
public static void main(String[] args) {
Stack<Integer> st = new Stack<Integer>();
st.
package com.ssm.cts.test;
import java.util.Enumeration;
import java.util.Vector;
public class ClassTest {
// 测试
public static void main(String[] args) {
Enumeration<String> elem;
Vector<String> site = new Vector<String>
package com.ssm.cts.test;
public class ClassTest {
// 测试
public static void main(String[] args) {
// 创建不同类型数组： Integer, Double 和 Character
Integer[] intArr = { 1, 2, 3, 4, 5 };
Double[] doubleArr = { 1.1, 2.2, 3.3, 4.4 };
Character[] ch
package com.ssm.cts.test;
public abstract class Bike {
private String name;
public abstract void start();
}
package com.ssm.cts.test;
public class MotoBike extends Bike {
@Override
public void start() {
System.out.println(“启动”);
}
使用 implements 关键字可以变相的使java具有多继承的特性，使用范围为类继承接口的情况，可以同时继承多个接口（接口跟接口之间采用逗号分隔）。
package com.ssm.cts.test;
public interface ICar {
public void start();
public void stop();
}
package com.ssm.cts.test;
public interface ICarFly {
public void
package com.ssm.cts.test;
public class Car {
public String code;
private String name;
public Car(String _name) {
super();
this.name = _name;
}
public void start() {
System.out.println(name + “启动”);
}
public void stop() {
Syste
package com.ssm.cts.test;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.Map;
import java.util.
package com.ssm.cts.test;
public class ClassTest {
// 测试
public static void main(String[] args) {
StringBuffer sb = new StringBuffer(“网址：”);
sb.append(“idodo”);
sb.append(“.xin”);
System.out.println(sb);
}
}
package com.ssm.cts.test;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.Map;
import java.util.Stack;
import java.util.Vector;
public class ClassTest {