How do I auto-fill fields from a lookup, or fill a lookup automatically without the user picking?

Short answer: Select every column you need in one lookup field, then read each into another field with a formula like Lookup_Field.Column. To fill the lookup without the user picking, add a filter and turn on Automatically select the first value based on the filters.

Why it happens

• A lookup brings in only the columns chosen under Select fields to use in this lookup.
• Other fields don't fill themselves; each needs a formula that points at the lookup column.

How to fix it

To fill other fields from a lookup:

1. In the lookup field, pick the flow and select all needed columns under Select fields to use in this lookup. You don't need a second lookup.
2. In each target field, enter a formula such as Material_Lookup.Name_of_Material. It fills when a value is picked.
3. To total a number from a lookup, put Lookup_Field.Amount in a Number field and aggregate that field.

To fill the lookup automatically:

1. Add a filter that matches a dataset column to a form field, for example Unit equal to the field Unit.
2. Turn on Automatically select the first value based on the filters.

Common variations:

• From a dropdown: make a dataset with the key and related columns, use it as the dropdown's source, then add an auto-select lookup filtered on that dropdown.
• Logged-in user's details: keep user emails and details in a dataset, filter on the creator's email, and read values with Lookup.Address.
• Initiator in a User field: add a hidden text field with _created_by.Name, filter the User field on Name equal to that field, and turn on auto-select.
• Chained lookups: copy the first lookup's value into a text field, such as Lookup1.Column, and filter the second lookup on that text field.
• Search finds too much: search runs across the columns shown. Remove extra columns from Fields to display and read them with a formula instead.

See lookup field and user field.