public Part AddSelect(string value, string name)
 {
     var part = new Part(value, name);
     Select.Add(part);
     return part;
 }
 public Part AddHaving(string value, string name)
 {
     var part = new Part(value, name);
     Having.Add(part);
     return part;
 }
 public Part AddOrderBy(string value, string name)
 {
     var part = new Part(value, name);
     OrderBy.Add(part);
     return part;
 }
 public Part AddGroupBy(string value, string name)
 {
     var part = new Part(value, name);
     GroupBy.Add(part);
     return part;
 }