To select one or more columns, send the Select Columns message to the data table.
dt = Open( "$SAMPLE_DATA/Big Class.jmp" );
clist = {:Height, :Weight};
dt << Select Columns( clist );
To select all columns, send the Select Columns message with the All argument to the data table.
dt = Open( "$SAMPLE_DATA/Big Class.jmp" );
dt << Select Columns( all );