I would like to compare / validate if the gift card number is valid

I would like to compare / validate if the gift card number is valid when the customer makes a booking.
I have two tables. The Giftcard table contains, among other things, the column ID that I want to compare with the booking number field that you enter in the form. I can't find any guide on this. Do you have any tips on how to do this?

Add a recordset to the page and filter it with the entered gift card number and see if there is a result or not. Then you can show an error for invalid card number if the recordset doesn't show a result.

I'm not sure if I understand correctly. I created a recordset that I filtered (right Join !?) that shows cardnumberID from both columns:
Here is the recordset:

SELECT Giftcard.GiftcardID, Booking.BookingGiftcardnoID
FROM Giftcard RIGHT OUTER JOIN Booking ON Giftcard.GiftcardID = Booking.BookingGiftcardnoID
Then, how do I compare / validate when the form field is filled in?

Add a WHERE clause to the recordset to filter based on the entered value from the form. Then you can use server validation to validate the ->TotalRows value from the recordset to ensure it is a valid entry.

I don't really understand how this Server Validation works.
I have created an pages from DataAssist where, there among other things, the gift card numbers exist.
First question: I can no longer change regular expression through any behavior. Is this correct? DataAssist builds this at the same time. But I must be able to change this afterwards, right?
Second: Can I change the look of JQuery Validation afterwards? Or remove it completely, to use Bootstrap's validation instead?
This is a side track to the post, but I would like to know the answers.
The main question is how to do what you describe. I have searched the Internet and searched your website forums and tutorials, but I am not wise in how to do this. A little frustrated!

First question: I can no longer change regular expression through any behavior. Is this correct? DataAssist builds this at the same time. But I must be able to change this afterwards, right?

Yes. You can edit the Server Validation server behavior to add Regular Expression validation after running the wizard. Regular Expression validation isn't exposed in the wizard itself.

Second: Can I change the look of JQuery Validation afterwards? Or remove it completely, to use Bootstrap's validation instead?

Yes and yes. You can change the look by updating the CSS file that is created or changing the javascript settings depending on what exactly you are trying to change. You can also remove it entirely by deleting the associated script tags at the bottom of the page.

Question 1: I can't find where to change this from wizard? I know I can change the pattern, but then I need to know how to format this :)
Question 2: I mean I want to change the Error format, like what you can choose from Form Settings in DataAssist. Can I do this after from any wizard?

You can't change it from the wizard. You would have to update the Server Validations server behavior after application.

Yes, you can change the error format in the code directly or by going to Webassist->Forms->Validation->JQ Validation

Good to know. Thanks!

I don't know what I'm looking for in your attached file. What is it you are trying to do exactly? Where are you getting stuck? If you give specific details and ask a specific question then I can try to answer it.