Validation - Help required

Hi,
I am fairly new to php3 and mysql. I would like to know how it is possible to make sure that only unique field entries can be made (ie. if the telephone number 123456 is already taken it cannot be registered again). I would much appreciate any help.
Thanks

A couple of options:
1. When processing a form, consider which fields need to be validated, and what sort of validation is required. So, if telephone numbers (to use your example) must be unique, you validate this input by doing a lookup on the relevant table to see if any records exist with the same tel number, eg.
$query ="select tel_no from addresses where tel_no=$new_tel LIMIT 1";
$result = mysql_query($query);
$count = mysql_num_rows($result);
if ($count==1):
echo "oops - duplicate tel no";
else:
echo "new tel is fine";
endif;

2. You can define a field on a MySQL table to be unique. If anyone tries to enter a duplicate, MySQL spits the dummy.


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