mysql基础知识

<?php/** * Created by PhpStorm. * User: dllo * Date: 16/8/11 * Time: 上午9:06 */header("Content-type:text/html;charset=utf-8");// 1. 连接服务器$mysql =  mysql_connect("localhost","root","");if ($mysql){    echo "success";    // 2. 选择数据库    $db = mysql_select_db("0503");    if ($db){        echo "0503 open success";        // 显示中文        mysql_query("set names utf8");//        $sql = "SELECT * FROM user";        // limit 查找多少个//        $sql = "SELECT * FROM user LIMIT 2";        // 按条件查找//        $sql = "SELECT * FROM user WHERE id < 6";//        $sql = "SELECT * FROM user WHERE username = 'kitty'";        // 排序 DESC倒序//        $sql =  "SELECT * FROM user ORDER BY id DESC";        // 排序 DESC正序//        $sql =  "SELECT * FROM user ORDER BY id ASC";        // 非//        $sql = "SELECT * FROM user WHERE NOT username = 'kitty'";        // AND 用来连接两个并列的条件,OR表示或//        $sql = "SELECT * FROM user WHERE id < 6 AND username = '春雨'";//        $result = mysql_query($sql);//        while($row = mysql_fetch_assoc($result)){//             print_r($row);//          }        // 插入//        $sql = "INSERT INTO user (id,username,password,tel) VALUES (NULL,'dog','789','1888888888')";//        mysql_query($sql);//        echo mysql_insert_id();        // 修改//        $sql = "UPDATE user SET username='cat',password = '6548' WHERE id = 7";//        mysql_query($sql);        // 受影响的行数//        if (mysql_affected_rows() > 0){//            echo "更新成功";//        };        // 删除        $sql = "DELETE FROM user WHERE username = '春雨'";        mysql_query($sql);        echo mysql_affected_rows();    }else{        echo "0503 open fail";    }}else{    echo "fail";}