SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 2)
   ExpressionList (children 1)
    Identifier a
   TablesInSelectQuery (children 1)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      Subquery (children 1)
       SelectWithUnionQuery (children 1)
        ExpressionList (children 1)
         SelectQuery (children 2)
          ExpressionList (children 1)
           Asterisk
          TablesInSelectQuery (children 1)
           TablesInSelectQueryElement (children 1)
            TableExpression (children 1)
             Subquery (children 1)
              SelectWithUnionQuery (children 1)
               ExpressionList (children 1)
                SelectQuery (children 2)
                 ExpressionList (children 1)
                  Asterisk
                 TablesInSelectQuery (children 1)
                  TablesInSelectQueryElement (children 1)
                   TableExpression (children 1)
                    TableIdentifier columns
