Problem...urgent solution needed

Question

The problem is... table A and table B are related with B as parent table and A child. The value of id (primary key) of table B needs to be populated with the column Bid when the following where condition satisfies.
A.x=B.x and A.y=B.y and A.z=B.z for every value of A
My problem is to create either a procedure, a function or a package which populates the value of B.id in table A with the above where condition for id value of A
I created a function which gives me the return value of Bid but unable to update the table as several ids of table A have the same value of Bid.
select A.id into bid from A,B where A.x=B.x and A.y=B.y and A.z=B.z;
return bid;
but in the same function I am unable to update
update A set bid=bid;
taking the return value from the function. I am unable to understand why? I am pretty weak in pl/sql kindly help me if am making some mistake. I NEED HELP FAST...THANKS IN ADVANCE
Can anyone suggest me the solution?

Answer 1

Thank you so much. I tried the update statement in two ways
1)by putting just the update statement in the function. it gave an error which says
4/1 PL/SQL: SQL Statement ignored
5/23 PL/SQL: ORA-00925: missing INTO keyword
2) I tried my another function where i retrieve the value of
begin
SELECT a.ID INTO V_a_ID
FROM a,
b
WHERE a.x= p_ID
AND a.y = code
AND upper(TRIM(a.z)) = upper(p_S_NAME)
AND (to_number(nvl(P_H_N,'0'))
BETWEEN to_number(a.h) AND
to_number(a.hb))
AND substr(P_q,1,5) = substr(a.q,1,5)
AND upper(P_r) = upper(a.r) and b.id=bid
RETURN V_a_ID;
update a set adrlib_id=(select b.id from b where a.x=b.x and a.y=b.y and a.z = b.z and (a.r between b.r and b.r1));
in the second instance, the retrieval of bid works fine but the update is ignored. please suggest. I also want to mention that for every value of a.id there are more than one values of bid. so the update will return more than one rows. kindly help.