Check for duplicates before inserting

Question

Before inserting into the database, I\'m using the following code to check for duplicates. To me, a duplicate is only considered a duplicate when name, de

Answer 1

In short you need to do your checking through PHP and you also need to add a composite unique constraint in your MySQL table to get the best of both worlds.

it would be good if we broke down your question into two separate questions.

1- How do I check duplicates using PHP and notify about the user before executing query? 2- How do I specify a composite unique constraint in MySQL?

First, you need a simple PHP function to check whether this record exist in the DB or not, like the one below:

function is_exist($table, $data){
    $sql = "SELECT * FROM `" . $table . "` WHERE ";

    foreach ($data as $key => $val) :
    $sql .= "`$key`='" . $val . "' AND ";
    endforeach;

    $sql = substr($sql,0, -5);

    $result = $mysql_query($sql);
    $count = $mysql_num_rows($result);

    return ($count > 0) ? true: false;
}   

You should call your PHP function like this way below:

    $data = array('column1'=>$_POST['value'],'column2'=>$_POST['value'], ...);

    if(is_exist($data)){
      // Print your error message
    }else{
     // Run your insert query
    }

This way you can prevent duplicates before going to the MySql Database, but in order to have a duplicate free database, you need to add a composite unique constraint in your MySQL table.

This simple SQL command can do the trick:

alter table `tablename` add unique index(name, description, manufacturer, city, price, enddate);

I hope that helps, if I mess anything please burden me.