create or replace function greatest_common_div(n1 number, n2 number)

return number

as

ret number;

begin

with NumberSet as (

select column_value Element from table(sys.odcinumberlist( n1, n2 ))

), Integers as (

select level num# from dual connect by level <= least( n1, n2 )

)

select max(Divisor) into ret

from (

select Divisor

from (

select num# as Divisor from Integers

where num# <= (select min(Element) from NumberSet)

), NumberSet

where mod(Element, Divisor)=0

group by Divisor

having count(*) = (select count(*) from NumberSet)

);

return ret;

end;

/

select greatest_common_div(15,123) from dual;

3

And a 11.2 version. Idea borrowed from http://wiki.postgresql.org. This is a better performing one as it handles only two numbers.

create or replace function greatest_common_div2(n1 number, n2 number)

return number

as

ret number;

begin

WITH t(a,b) AS (

select n1, n2 from dual

UNION ALL

SELECT b, mod(a,b) FROM t

WHERE b > 0

)

SELECT a into ret

FROM t

WHERE b = 0

;

return ret;

end;

/

And the same without pl/sql to sql context switch.

*Added 12.9.2011*

create or replace function greatest_common_div3(n1 number, n2 number)

return number

as

ret number;

begin

ret := n1;

if (n2 != 0) then

ret := greatest_common_div3(n2,mod(n1,n2));

end if;

return ret;

end;

/

with numbers as (select level num from dual connect by level < 100)

, test as (

select a.num a

, b.num b

, greatest_common_div(a.num,b.num) gcd

, greatest_common_div2(a.num,b.num) gcd2

, greatest_common_div3(a.num,b.num) gcd3

from numbers a, numbers b

)

select * from test where gcd!=gcd2 or gcd!=gcd3

;

*Update 28.3.2011*

Added an user defined aggregate also.

CREATE OR REPLACE TYPE t_gcd_agg AS OBJECT

(

g_number number,

STATIC FUNCTION ODCIAggregateInitialize(sctx IN OUT t_gcd_agg)

RETURN NUMBER,

MEMBER FUNCTION ODCIAggregateIterate(self IN OUT t_gcd_agg,

value IN number )

RETURN NUMBER,

MEMBER FUNCTION ODCIAggregateTerminate(self IN t_gcd_agg,

returnValue OUT number,

flags IN NUMBER)

RETURN NUMBER,

MEMBER FUNCTION ODCIAggregateMerge(self IN OUT t_gcd_agg,

ctx2 IN t_gcd_agg)

RETURN NUMBER

);

/

CREATE OR REPLACE TYPE BODY t_gcd_agg IS

STATIC FUNCTION ODCIAggregateInitialize(sctx IN OUT t_gcd_agg)

RETURN NUMBER IS

BEGIN

sctx := t_gcd_agg(NULL);

RETURN ODCIConst.Success;

END;

MEMBER FUNCTION ODCIAggregateIterate(self IN OUT t_gcd_agg,

value IN number )

RETURN NUMBER IS

BEGIN

SELF.g_number := greatest_common_div3(case when self.g_number is null then value else self.g_number end, value);

RETURN ODCIConst.Success;

END;

MEMBER FUNCTION ODCIAggregateTerminate(self IN t_gcd_agg,

returnValue OUT number,

flags IN NUMBER)

RETURN NUMBER IS

BEGIN

returnValue := SELF.g_number;

RETURN ODCIConst.Success;

END;

MEMBER FUNCTION ODCIAggregateMerge(self IN OUT t_gcd_agg,

ctx2 IN t_gcd_agg)

RETURN NUMBER IS

BEGIN

SELF.g_number := greatest_common_div3(case when self.g_number is null then ctx2.g_number else self.g_number end

, case when ctx2.g_number is null then self.g_number else ctx2.g_number end);

RETURN ODCIConst.Success;

END;

END;

/

CREATE OR REPLACE FUNCTION gcd (p_input VARCHAR2)

RETURN VARCHAR2

PARALLEL_ENABLE AGGREGATE USING t_gcd_agg;

/

select gcd(column_value) from table(sys.odcinumberlist(4,8,34));

2

with test as (

select 'a' a, 4 n from dual union all

select 'a' a, 6 n from dual union all

select 'b' a, 30 n from dual union all

select 'b' a, 60 n from dual union all

select 'b' a, 96 n from dual

)

select a,gcd(n)

from test

group by a;

a 2

b 6