Do I need to add a connection field to both of the objects I want to connect together?
No, you only need one connection field. Adding a connection field to both objects can confuse things in your live application.
Which object should I add the connection to?
For one-to-many connections, it generally works best to add the connection to the many, or "child" object.
For many-to-many, add the connection to the object that you want to select the connected record from in the Live App. For example, you may have a many-many relationship between Projects and Managers. Which record do you want to edit to connect to the other record? If you want to be able to add Managers to Projects from the Project details page, add the connection field to the Projects object.
Do I need to track unique ID or key fields?
No, Knack manages all the connections behind the scenes without needing key or ID fields.
If I delete a parent record will all the connected child records also be deleted?
No, the child records will not be deleted.
How do I delete a connection?
From the data tab in the Knack builder, select the object whose connection you would like to delete. Locate the connection field among your list of fields, hover your mouse over it, and click the x on the right side:
My connection field shows as undefined.
A record in one object is connected, but the connection field shows "Undefined" instead of the connected record.
To fix this, go to the settings tab of your connected object, in the Data section of the Builder. Change the Display Field, save, and change the Display Field back to what you want.
You will now see the connected record display properly in the original object.
How can I display multiple fields from one object in a connection field?
You can customize what field from a connected object shows in a connection field via the display field.
To show multiple fields from one object in the display field, use a text formula to combine the fields into one. The text formula can then be used as the display field. This guide explains the process of setting this up: How to Show Multiple Fields in Your Connection Dropdown