Question

I am querying a large number of codes from my database, and need to have some validation before a user can input another code in to the database.

An example code would be this:

TD-BR-010212-xxxxxxxx

Where TD represents a promotion, BR represents a place, the numbers represent a date, and the rest are random.

My problem is that before the code is entered into the DB, I want to check to see if the date and place for that code already exists, as they should not be allwed to enter a code from the same place and date.

I assume it would be something within a loop as I already have:

$location_part_of_td = $code[2].$code[3];
$date_part_of_td = $code[4].$code[5].$code[6].$code[7].$code[8].$code[9];

$trade_day_result = mysql_query('SELECT * from wp_scloyalty WHERE promotion_type = trade-day') or die(mysql_error());  // Pulls all trade day codes from the database and checks the date part of the code. 

// the date part exists with the same area part, user cant redeem.
while($info = mysql_fetch_array( $trade_day_result )) 
{ 

     $code = $info["product"];

} 

But Im just not sure about the best way to check the strings..

Answer 1

You can use a MySQL LIKE clause to get entries in your DB that resemble your code.

Example:

$code_exists = mysql_query( 
      "SELECT 'a' FROM table_name WHERE column_name LIKE 'TD-BR-010212-%'"
);
if(mysql_num_rows($code_exists) > 0) {
    // The specified place/date is taken
} else {
    // No promotion at place BR on the specified date.
}

The ‘%’ is used as a wildcard in SQL LIKE clauses.