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DiPaspafe
Asked: 2022-10-21 09:50:39 +0800 CST 2022-10-21 09:50:39 +0800 CST

How do I make a String value non-repeatable in MySQL?

  • 772

I want that when you try to do an INSERT, but the value of a specific variable is already registered, it shows an error.

For example: | user | e-mail | | -------- | -------------- | | Joseph | [email protected] | | Rex | [email protected] |

If I enter this code it should show an error because the value is already assigned to a user.

INSERT INTO `users` (`usuario`, `email`) VALUES ("Eduardo", "[email protected]");

I hope I explained myself well, I'm new and this would help me a lot.

mysql

1 Answers

  1. Best Answer

    You can first request the registered data with SELECT and then compare the entered data with the registered data and thus if any of the entered data is repeated, show a message that the data already exists, and if not, save the data with INSERT , as I did next:

    <?php
     $query = mysqli_query("SELECT 'usuario', 'email' FROM users");
     $result = mysqli_num_rows($query);
    
     $repeat = 0;
    
     if($result > 0)
     {
          while($data = mysqli_fetch_array($query))
          {
               if(hash_equals($data['usuario'], "Eduardo") || hash_equals($data['email'], "[email protected]")) {
                    $repeat = 1;
                    break;
               }
          }
          if($repeat == 0) {
               $sentenciaSQL = $conexion->prepare("INSERT INTO `users` (`usuario`, `email`) VALUES ("Eduardo", "[email protected]")");
               $sentenciaSQL->execute();
               $data=$sentenciaSQL->fetch(PDO::FETCH_LAZY);
          }else {
               echo "Estos datos ya se encuentran registrados.";
          }
     }
?>

    You can also do a SELECT with a WHERE to search directly for the data in the table:

    <?php

 $sentenciaSQL = $conexion->prepare("SELECT* FROM users WHERE email=:email");
 $sentenciaSQL->bindParam(':email','[email protected]');
 $sentenciaSQL->execute();
 $data=$sentenciaSQL->fetch(PDO::FETCH_LAZY);

 if($data['password'] == "[email protected]")
 {
      echo "Estos datos ya se encuentran registrados.";
 }else {
      $sentenciaSQL = $conexion->prepare("INSERT INTO `users` (`usuario`, `email`) VALUES ("Eduardo", "[email protected]")");
      $sentenciaSQL->execute();
      $data=$sentenciaSQL->fetch(PDO::FETCH_LAZY);
      echo "Datos registrados correctamente.";
 }

?>

    Hope this can help you ;).

    • -1