SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 3)
   ExpressionList (children 1)
    Asterisk
   TablesInSelectQuery (children 1)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      TableIdentifier merge
   ExpressionList (children 2)
    OrderByElement (children 1)
     Identifier _part_index
    OrderByElement (children 1)
     Identifier x