/**
   * @param tableName
   * @param columnName
   * @param seq
   */
  public void addForeignKey(String tableName, String columnName, String parentColumn, Integer seq) {
    ForeignKey tbl = null;
    if (associatedTables.containsKey(tableName)) {
      tbl = (ForeignKey) associatedTables.get(tableName);
    } else {
      tbl = new ForeignKey(parentTable, tableName);
      associatedTables.put(tableName, tbl);
    }

    tbl.addColumn(columnName, parentColumn, seq);
  }
 /**
  * @param col
  * @param seq
  */
 public void addColumn(String col, String parentCol, Integer seq) {
   columns.put(seq, col);
   parentColumns.put(seq, parentCol);
 }