Duplicate values in database

[palpie]

I want to store two values in a database. A random number and a string. The string can sometimes be the same as other rows. I want the random number, when it's being stored, to be checked if it's an unique value in the table. If it is, it shall be stored and the number shall be printed on the screen. If not, the number shall change to another number, which is unique. Then the variable, which the number is stored in, should change to the new number.

Messy description? Perhaps. Please try and help my anyway.

[kparker]

The best way is to just define a UNIQUE index on the column containing the random number. Then just go ahead and INSERT your candidate row; if it fails you know there's a dup and you can generate a new random value and try that.

[palpie]

Ok. Could you help me a bit with some code? Shall I do something like "on error" after the INSERT? How do I do this?

[Anon]

I suppose, you can just write:

while (!$res){
mt_srand((double)microtime()*1000000);
$rand = mt_rand();
$qwr="INSERT INTO mytable (field) VALUES ('$rand')";
$res=mysql_query($qwr);
}