I was recently building a Power App for a work project and needed to change the secondary text in a combo box to display “Account Name” from the Accounts table. The only field available was “Account ID” from the Projects table.

Here is how you join two tables in Power Apps using the AddColumns function.

To break it down: AddColumns(Table1, “New Column Name”, LookUp(Table2, ‘Column We Want to Look Up’ = Table2[@Table We Have to Compare Against], ‘Column We Want To Return’))

AddColumns(
    Projects,
    "Account Name",
    LookUp(
        Accounts,
        'Account ID' = Projects[@Account],
        'Account Name'
    )
)

We’ve now added a new column called “Account Name” (from the Accounts table) to the Projects data source in our combo box.