UNION two DT and fill missing columns in DT2 with NULL values

Dear community,

We are currently facing the task to union two data tables where the first DT has much more columns than the second DT but all of those columns should be kept after the UNION and all columns that are not in DT2 should be filled with NULL values.
Currently, the approach would be to work with the Query Helper to find the different columns and set up an appropriate SELECT statement. Anyway (also for future OD users), I was wondering if there is an alternative way or Best practice.