How do you ck to make sure an entry is not already in a mysql table from a form?

Phrank

Lets say I am building up a list of salespersons for a company. I am using a Form and the first field on the form
is the salespersons initials. I know I can use onBlur() in the input field and jump to a Javascript function as
soon as I have left the initials field.

In that Javascript function am I supposed to be able to query a mysql table to see if the initials are already there
(already been used)?

I can load the initials from all the salepersons from the salespersons table in a PhP array at the beginning of the form.
Can you ck against that list via Javascript?

Do you just tell mysql that the initials are UNIQUE and work with error routines when a user types some initials that already exists?

How do you guys do it?

traq

Phrank;11019863 wrote:
In that Javascript function am I supposed to be able to query a mysql table to see if the initials are already there
(already been used)?

... javascript can't query MySQL.

Phrank;11019863 wrote:
I can load the initials from all the salepersons from the salespersons table in a PhP array at the beginning of the form.
Can you ck against that list via Javascript?

... javascript can't use PHP variables
(they don't even exist by the time js executes - PHP is server-side, js is client-side. time to learn the basics!).

IF you print the values into a javascript array, then yes (but it's not necessarily the best approach).

Phrank;11019863 wrote:
Do you just tell mysql that the initials are UNIQUE and work with error routines when a user types some initials that already exists?

you can, yes.

Phrank;11019863 wrote:
How do you guys do it?

You can use javascript to make an ajax call to a php script that checks if the option already exists in the DB.

You should also implement this check when you process the form and insert the data (after all, you should never trust user input).

Bonesnap

Simply put, you can deal with this in three ways:

1) As mentioned, you can make an AJAX call via JavaScript to a PHP script that can check the database if the initials exist. If they do then create an appropriate message/alert for the user.
2) You can check the initials in the database when you submit the form. If they exist, again, present an appropriate response to the user.
3) You can make the column unique and when the form is submitted, check for a particular error code (for a unique record).

Which route I take really depends on the project but I try to combine at least two of the three methods (usually methods 1 and 2). For an ironclad approach I would do them all.