You can check if columns are numeric before concatenation and update final result accordingly. Or you could go over character columns after you are done concatenating and change them. I haven't tried this exact method myself (<< fail on conversion), but I think it should work fine
Names Default To Here(1);
dt = New Table("My Table",
New Column("col1", Character, "Nominal", Set Values({"123", "456", "abc", "789", "", "def"})),
New Column("col2", Character, "Nominal",Set Values({"123", "456", "789", "", "", ""}))
);
For Each({colname}, dt << Get Column Names("Character", "String"),
r = Column(dt, colname) << Set Data Type("Numeric", <<Fail On Conversion Error, <<Return Failed Rows);
If(N Items(r) == 0,
Column(dt, colname) << Set Modeling Type("Continuous");
);
);
-Jarmo