code: public FKeyModel singleFKey(String... refTableAndColumns) {
  		makeSureTableModelExist();
  		if (refTableAndColumns == null || refTableAndColumns.length > 2)
  			throw new DialectException(
  					"singleFKey() first parameter should be table name, second parameter(optional) should be column name");
  		return this.tableModel.fkey().columns(this.columnName).refs(refTableAndColumns);
  	}
docs: A shortcut method to add Foreign constraint for single column, for multiple
  columns please use tableModel.fkey() method instead