How to add new field to an existing database?

Good afternoon,
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I have to create a new field in a form which is already connected to a database.
What I have to do to add this nex field in the database ?
Thanks for your help.
Regards.
​
Virginie

Can you just use PHPMyAdmin?

Yes I thought about it but may be there is a better way without working directly in the database.
If someone knows...
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Regards

CF 6 has basic data table editing. But doing it properly is best.

Thank you for your help.