code: String getColIsNullable(int i) {
  
          ColumnSchema column = table.getColumn(i);
  
          return (column.isNullable() && !column.isPrimaryKey()) ? "YES"
                                                                 : "NO";
      }
docs: Retrieves whether the specified column is nullable. <p>
  
  If the column is nullable, "YES" is retrieved, else "NO". <p>
  
  @param i zero-based column index
  @return the nullability of the specified column