如何检查数据库中是否存在数据？

Question

如何检查数据库中是否已存在数据（$ chassis，$ pin），如果存在，我希望它将错误返回为“用户存在”。 我使用json显示错误，现在使用下面的代码插入数据，即使机箱和引脚已经存在于数据库中。

<?php 
session_start(); 

require("config/config.php"); 
date_default_timezone_set('Asia/Calcutta'); 
if (isset($_POST['user_submit'])) 
    $chassis = mysql_real_escape_string($_POST['chassis']); 
$pin   = mysql_real_escape_string($_POST['pin']); 
$title   = mysql_real_escape_string($_POST['title']); 
$fname   = mysql_real_escape_string($_POST['fname']); 
$lname   = mysql_real_escape_string($_POST['lname']); 
$email   = mysql_real_escape_string($_POST['email']); 
$mobile  = mysql_real_escape_string($_POST['mobile']); 
$dob   = mysql_real_escape_string($_POST['dob']); 
$anniversary = mysql_real_escape_string($_POST['anniversary']); 
$company  = mysql_real_escape_string($_POST['company']); 
$designation = mysql_real_escape_string($_POST['designation']); 
$home_business = mysql_real_escape_string($_POST['home_business']); 
$add1   = mysql_real_escape_string($_POST['add1']); 
$add2   = mysql_real_escape_string($_POST['add2']); 
$city   = mysql_real_escape_string($_POST['city']); 
$state   = mysql_real_escape_string($_POST['state']); 
$pincode  = mysql_real_escape_string($_POST['pincode']); 
$date   = date('y.m.d h:i:s A'); 

$hostname = ''; 
$database = ''; 
$username = ''; 
$password = ''; 

$conn = mysql_connect($hostname, $username, $password); 
if (!$conn) { 
    $json['error'] = "Unable to Connect server!" . mysql_error(); 
} 
if (empty($json)) { 
    mysql_select_db($database) or die("Unable to select database!" . mysql_error()); 
    $sql = mysql_query('SELECT chassis,pin FROM checking_chassis WHERE chassis="' . $chassis . '" && pin="' . $pin . '" '); 

    if (mysql_num_rows($sql) == 1) { 

     $sql1 = mysql_query('SELECT chassis,pin FROM taj_contact_info WHERE chassis="' . $chassis . '" && pin="' . $pin . '" '); 
     if (mysql_num_rows($sql1) == 1) { 
      $json['error'] = "User already exists"; 
      exit(); 
     } else { 
      $query = 'INSERT INTO taj_contact_info (chassis,pin,title,fname,lname,email,mobile,dob,anniversary,company,designation,home_business,add1,add2,city,state,pincode,date_added) VALUES("' . $chassis . '","' . $pin . '","' . $title . '","' . $fname . '","' . $lname . '","' . $email . '","' . $mobile . '","' . $dob . '","' . $anniversary . '","' . $company . '","' . $designation . '","' . $home_business . '","' . $add1 . '","' . $add2 . '","' . $city . '","' . $state . '","' . $pincode . '","' . $date . '")'; 

      $sql1 = mysql_query($query); 

      $message = "Thank you for registering. You can indulge in the fine dining experience with the Taj gift certificate, which will reach you within 30 days. Team Purple Club"; 

      $sms = "http://bulkpush.mytoday.com/BulkSms/SingleMsgApi?feedid=340479&UserName=&password=&sendername=PURPLE&To=" . $mobile . "&message=" . urlencode($message) . ""; 

      $work = file_get_contents($sms); 

      $json['success'] = "Successfully inserted"; 
     } 
    } else { 
     $json['error1'] = "Please enter valid chassis number and pin"; 

    } 

} 

echo json_encode($json); 
?> 

的Javascript

<script type="text/javascript"> 
    $(document).ready(function(){ 

     $("#user_submit_form").submit(function(){ 
      var user_data = $("#user_submit_form").serialize(); 

           var mobile = new Array();                
               mobile = $('#mobile').val().split(""); 

               var pincode = new Array();               
               pincode = $('#pincode').val().split(""); 

               if($('#chassis').val() =='') 
               {            
                       alert('Please enter chassis'); 
               }    
               else if ($('#pin').val() =='') 
               {            
                       alert('Please enter pin'); 
               } 


               else  { 

                       $.ajax({ 
                       type               : "post", 
                       url                : "validate_user.php", 
                       data               : user_data, 
                       dataType              : "json", 
                       success: function(json){ 

                           if(json.error) 
                           { 
                               alert(json.error) 
                           } 
                           else if(json.error1) 

                           { 
                               alert(json.error1) 

                           } 
                           else 
                           { 
                               alert(json.success) 
                               /*location.reload(); 

                               window.location="http://clps.cequitysolutions.com/taj/thankyou.php";*/ 

                           } 
                       } 


                       }); 


                       } 
     });     

       }); 
     function validateEmail(email) 
       { 
           var re = /^(([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;                        
           return re.test(email); 
       } 
</script> 

Answer 1

我会说你应该chassis和pin创建唯一索引。避免重复也正是为什么唯一索引存在：

alter table taj_contact_info add unique index(chassis, pin) 

现在你可以安全地运行您的插入查询：

$query = 'INSERT INTO taj_contact_info (chassis,pin,title,fname,lname,email,mobile,dob,anniversary,compa ... 

和检查后，如果记录已经插入：

if (mysql_affected_rows()>0) { 
    //success 
} else { 
    $json['error'] = "User already exists" 
} 

如果mysql_affected_rows返回-1，则插入脚本失败。如果（我猜）机箱无效，就会发生这种情况，就像空字符串一样。

Answer 2

为taj_contact_info表上的两列创建唯一索引。

ALTER TABLE taj_contact_info ADD UNIQUE INDEX uniqueindex (chassis,pin) 

，当您尝试插入正常后，在PHP中，你会得到一个重复键错误，你可以在PHP处理...如果你做一个SELECT查询

$sql = "insert into taj_contact_info set chassis='1234', pin='12345',etc..."; 
$result = mysql_query($sql); 
if (!$result) { 
    if (mysql_errno() == 1586) { 
     echo "ID is already in the database, user exists"; 
    } else { 
     die('Invalid query: ' . mysql_error()); 
    } 
} else { 
    echo "All cool, user inserted."; 
}