which are a special type of column whose values are automatically generated based on a user-specified function over other columns in the Delta table. You can use most built-in SQL functions to generate the values of these generated columns. For example, you can automatically generate a date column (for partitioning the table by date) from the timestamp column; any writes into the table need only specify the data for the timestamp column. You can create Delta tables with generated columns using SQL, Scala, Java or Python APIs.
https://docs.databricks.com/delta/delta-batch.html#use-generated-columns
