code: String getColumnName() {
          if (alias != null) { return alias; }
  
          if (selectExpression instanceof PropertyExpression) {
              return ((PropertyExpression) selectExpression).getColumnName();
          }
          if (selectExpression instanceof MetaExpression) {
              return ((MetaExpression) selectExpression).getColumnName();
          }
  
          return null;
      }
docs: ---------------------------------------------