docs: private String getWhere(V v) {
  		String sql = "";
  		if (this.checkValueNull(v.getValue())) {
  			if (this.ignoreNull == false) {
  				sql = "(" + v.getField() + " is null ) and ";
  			}
  		}
  		else {
  			sql = "(" + v.getField() + " " + v.getOperate() + " ?) and ";
  		}
  		return sql;
  	}