The closest that I have found is update. The difference between join and update is that join creates a new table whereas update adds the columns to the first table.
Col1 from table dt is the reference for col1 from table dt2.
Col2 is the columns with the values that we want to add to table 1.
dt << update (with (dt2), by matching columns (dt:col1==dt2:col1), add columns from update table(:col2));