DIY ANY_VALUE

I really like the ANY_VALUE aggregate function. But since it was added in Oracle 19c, I can’t use it in my Oracle XE database, as currently the latest version of XE is 18c.
So I decided to implement it as a user-defined function using the Oracle Data Cartridges Interface.

Note that this implementation is for VARCHAR2. If the function is used on other data types, the regular rules for implicit conversion apply.

    
SQL> create type any_value_string_t as object
  2  (
  3      v_value varchar2(4000),
  4      static function odciaggregateinitialize(sctx in out any_value_string_t) return number,
  5      member function odciaggregateiterate
  6      (
  7          self  in out any_value_string_t,
  8          value in varchar2
  9      ) return number,
 10      member function odciaggregatemerge
 11      (
 12          self in out any_value_string_t,
 13          ctx2 in any_value_string_t
 14      ) return number,
 15      member function odciaggregateterminate
 16      (
 17          self        in any_value_string_t,
 18          returnvalue out varchar2,
 19          flags       in number
 20      ) return number
 21  );
 22  /

Type created.

SQL> create type body any_value_string_t as
  2
  3      static function odciaggregateinitialize(sctx in out any_value_string_t) return number is
  4      begin
  5          sctx := any_value_string_t(null);
  6          return odciconst.success;
  7      end;
  8
  9      member function odciaggregateiterate
 10      (
 11          self  in out any_value_string_t,
 12          value in varchar2
 13      ) return number is
 14      begin
 15          if self.v_value is null then
 16              self.v_value := value;
 17          end if;
 18          return odciconst.success;
 19      end;
 20
 21      member function odciaggregateterminate
 22      (
 23          self        in any_value_string_t,
 24          returnvalue out varchar2,
 25          flags       in number
 26      ) return number is
 27      begin
 28          returnvalue := self.v_value;
 29          return odciconst.success;
 30      end;
 31
 32      member function odciaggregatemerge
 33      (
 34          self in out any_value_string_t,
 35          ctx2 in any_value_string_t
 36      ) return number is
 37      begin
 38          if self.v_value is null then
 39              self.v_value := ctx2.v_value;
 40          end if;
 41          return odciconst.success;
 42      end;
 43
 44  end;
 45  /

Type body created.

SQL> begin
  2    $IF DBMS_DB_VERSION.ver_le_18 $THEN
  3      execute immediate q''create function any_value (p_value varchar2) return varchar2
  4                           parallel_enable
  5                           aggregate using any_value_string_t;'';
  6      execute immediate q''grant execute on any_value to public'';
  7      execute immediate q''create public synonym any_value for any_value'';
  8    $ELSE
  9      raise_application_error(-20000,'ANY_VALUE is now supported by Oracle');
 10    $END
 11  end;
 12  /

PL/SQL procedure successfully completed.

Now any_value can be used just like any built-in aggregate function:

SQL> conn hr/hr
Connected.
SQL> select banner from v$version;

BANNER
------------------------------------------------------------------------------------------------------------------------
Oracle Database 18c Express Edition Release 18.0.0.0.0 - Production

1 row selected.

SQL> select d.department_id,
  2         any_value(d.department_name) department_name,
  3         count(*) number_of_employees
  4  from   employees   e,
  5         departments d
  6  where  d.department_id = e.department_id
  7  group  by d.department_id;

DEPARTMENT_ID DEPARTMENT_NAME      NUMBER_OF_EMPLOYEES
------------- -------------------- -------------------
           10 Administration                         1
           20 Marketing                              2
           30 Purchasing                             6
           40 Human Resources                        1
           50 Shipping                              45
           60 IT                                     5
           70 Public Relations                       1
           80 Sales                                 34
           90 Executive                              3
          100 Finance                                6
          110 Accounting                             2

11 rows selected.