SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 2)
   ExpressionList (children 1)
    Function plus (children 1)
     ExpressionList (children 2)
      ColumnsRegexpMatcher
      ColumnsRegexpMatcher
   TablesInSelectQuery (children 1)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      Subquery (children 1)
       SelectWithUnionQuery (children 1)
        ExpressionList (children 1)
         SelectQuery (children 1)
          ExpressionList (children 2)
           Literal UInt64_1 (alias a)
           Literal UInt64_2 (alias b)