java处理数据库的CRUD

package com.lhy.jdbc.util;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

/**
 *
 * 增删改查
 * @author hy
 * 
 */
public class CRUD {
    public static void main(String[] args) {
        //create();
        //read();
        //update();
        delete();
    
    }

    /**
     * 查询
     */
    static void read() {
        Connection conn = null;
        Statement stmt = null;
        ResultSet rs = null;

        try {
            // 建立连接，JdbcUtil工具类请看我的另一篇博客
            conn = JdbcUtil.getConnection();
            // 创建语句
            stmt = conn.createStatement();
            /**
             *  执行语句,一般不建议直接写select *，可读性不好。
             */
            rs = stmt.executeQuery("select * from user");

            // 处理结果
            while (rs.next()) {

                System.out.println(rs.getString("username") + "\t"
                        + rs.getString("password"));
            }

        } catch (SQLException e) {

            e.printStackTrace();
        } finally {
            JdbcUtil.close(rs);
            JdbcUtil.close(stmt);
            JdbcUtil.close(conn);
        }

    }
    /**
     * insert into插一条记录
     */
    static void create(){
        
        Connection conn = null;
        Statement stmt = null;
    
        try {
            // 建立连接
            conn = JdbcUtil.getConnection();
            // 创建语句
            stmt = conn.createStatement();
            
            String sql = "insert into user values('你好','147',1000)";
            
            //执行语句,返回值是int  几行被插入
            stmt.executeUpdate(sql);
            //int i = stmt.executeUpdate(sql);
            //System.out.println("i="+i);

        } catch (SQLException e) {

            e.printStackTrace();
        } finally {
            
            JdbcUtil.close(stmt);
            JdbcUtil.close(conn);
        }

    }
    
    
    
    
    /**
     * 更新
     */
    
    static void update(){
        
        Connection conn = null;
        Statement stmt = null;
        

        try {
            // 建立连接
            conn = JdbcUtil.getConnection();
            // 创建语句
            stmt = conn.createStatement();
            // 执行语句
            String sql = "update user set money = money + 100";
        //    int i = stmt.executeUpdate(sql);
           // System.out.println("i="+i);

        } catch (SQLException e) {

            e.printStackTrace();
        } finally {
            
            JdbcUtil.close(stmt);
            JdbcUtil.close(conn);
        }

    }
    
    static void delete(){
        

        Connection conn = null;
        Statement stmt = null;
    

        try {
            // 建立连接
            conn = JdbcUtil.getConnection();
            // 创建语句
            stmt = conn.createStatement();
            // 执行语句
            String sql = "delete  from user where money <600";
            int i = stmt.executeUpdate(sql);
            System.out.println("i="+i);

        } catch (SQLException e) {

            e.printStackTrace();
        } finally {
            
            JdbcUtil.close(stmt);
            JdbcUtil.close(conn);
        }
    }
}

 

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