两个表中查询出不同的数据

1.有两个表,表的属性都有：id,name,sex,age；第一个表有700条数据，第二个表有500条数据，其中两个表中有300条是name相同的，如何把两个表中不相同的数据取出来，怎么做？

答：

首先建2个表student1和student2，各有以上的四个字段。

我用mysql5.1数据库测试

1.SELECT DISTINCT  t.* FROM (SELECT * FROM student1  UNION (SELECT * FROM student2 )) AS t
2.SELECT * FROM student1 UNION (SELECT * FROM student2 WHERE NAME NOT IN (SELECT NAME FROM student1))

以上两个sql都可以查到。

数据库连接

package com.db;


import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;

import com.mysql.jdbc.PreparedStatement;

public class DBConnection {
	//从db.properties获取属性然后使用
	public String[] getDBProperties(String dbtype){
		Properties prop=new Properties();
		String driver = null,url=null,username=null,password=null;
		try {
			String type=changDBType(dbtype);		
			String[] dbCon=new String[]{
					type+"_Driver",
					type+"_Url",
					type+"_Username",
					type+"_Password"};
			prop.load(ClassLoader.getSystemResourceAsStream("db.properties"));
			driver=prop.getProperty(dbCon[0]);
			url=prop.getProperty(dbCon[1]);
			username=prop.getProperty(dbCon[2]);
			password=prop.getProperty(dbCon[3]);		
		} catch (IOException e) {
			e.printStackTrace();
		} catch (Exception e) {
			e.printStackTrace();
		}	
		String db[]=new String[]{driver,url,username,password};
		return db;
	}
	//首先把字符串的第一个字符变大写，其他的变小写
	public String changDBType(String dbtype) throws Exception{
			if(dbtype.isEmpty()){
				throw new Exception("dbtype字符串为空");	
			}else{
				return String.valueOf(dbtype.charAt(0)).toUpperCase().concat(dbtype.substring(1).toLowerCase());
			}	
	}
	Connection con;
	Statement stat;
	public Connection getCon(String driver,String url,String username,String password){
		try{
	
			Class.forName(driver);
			con=DriverManager.getConnection(url,username,password);
			stat=con.createStatement();	
		}catch(SQLException e){			
			System.out.println("数据库连接SQL异常");
		} catch (ClassNotFoundException e) {
			System.out.println("数据库连接类找不到异常");
			e.printStackTrace();
		}
		return con;
	}
	public static void main(String args[]){
		DBConnection dbc=new DBConnection();
		String db[]=dbc.getDBProperties("mysql");

		Connection con=dbc.getCon(db[0], db[1], db[2], db[3]);
		String sql1="insert into student1(id,name,sex,age) values(?,?,?,?)";
		String sql2="insert into student2(id,name,sex,age) values(?,?,?,?)";
		try {
			PreparedStatement pstmt=(PreparedStatement) con.prepareStatement(sql2);
			for(int i=301;i<=500;i++){
				pstmt.setObject(1, i);
				pstmt.setObject(2, "郑爽"+i);
				pstmt.setObject(3, "女"+i);
				pstmt.setObject(4, 20);
				pstmt.execute();
			}
			
	
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		


		
}

db.properties

Mysql_Driver=com.mysql.jdbc.Driver
Mysql_Url=jdbc:mysql://localhost:3306/itcast?useUnicode=true&characterEncoding=UTF-8
Mysql_Username=root
Mysql_Password=liming

Oracle_Driver=oracle.jdbc.driver.OracleDriver
Oracle_Url=jdbc:oracle:thin:@127.0.0.1:1521:orcl
Oracle_Username=ytpms
Oracle_Password=ytpms