How to validate data after update in oracle - sql

Question

I have two tables A and B which are not related.
SQL> select * from A;
OLD_ID R_ID
---------- ----------
TA-BC 1
TB-BC 2
TC-BC 3
TD-BC 4
TE-BC 5
TF-BC 6
TG-BC 7
8
SQL> select * from B;
NEW_ID OLD_ID S_CD
---------- ---------- -----
1 TA-BC A
2 TB-BC B
3 TC-BC C
4 TD-BC A
5 TE-BC B
6 TF-BC F
7 TG-BC C
8 TH-BC B
I need to update column "old_id" in table A with corresponding "new_id" values from table B where A.OLD_ID = B.OLD_ID.
I have written something like below. The data in table A and B has around 1 million records the one i gave above here is sample data. Since the data volume is high am updating for every 25k records and commiting it in a loop.
DECLARE
v_cnt number := 1;
BEGIN
WHILE v_cnt > 0 LOOP
UPDATE /*+ parallel(A 10) */ A a
SET a.old_id =
(SELECT DISTINCT new_id
FROM B b
WHERE b.old_id = a.old_id)
WHERE EXISTS
(SELECT 1
FROM B b1
WHERE b1.old_id = a.old_id and ROWNUM < 25000;
v_cnt := SQL%ROWCOUNT;
COMMIT;
END LOOP;
END;
/
I would like to know how can i print how many records got updated and how can i validate whether all the records in table A which has the matching record in table B with old_id has got updated correctly or not. What is the query i can write before/after the update statement to validate if table A "old_id" column has been updated correctly with values from table B "new_id" columns
Below is the table creation script.
create table A(old_id varchar2(10),r_id number);
insert into A values ('TA-BC',1);
insert into A values ('TB-BC',2);
insert into A values ('TC-BC',3);
insert into A values ('TD-BC',4);
insert into A values ('TE-BC',5);
insert into A values ('TF-BC',6);
insert into A values ('TG-BC',7);
insert into A(r_id) values(8);
commit;
create table B(new_id number,old_id varchar2(10),s_cd varchar2(5));
insert into B values (1,'TA-BC','A');
insert into B values (2,'TB-BC','B');
insert into B values (3,'TC-BC','C');
insert into B values (4,'TD-BC','A');
insert into B values (5,'TE-BC','B');
insert into B values (6,'TF-BC','F');
insert into B values (7,'TG-BC','C');
insert into B values (8,'TH-BC','B');
commit;

Answer 1

I don't see why you are replacing OLD_ID with NEW_ID when they are different data types: OLD_ID is char and NEW_ID is an integer.
It would be better to add a new field (column) to the table to store NEW_ID and update that.
You can then check the mapping of old to new has been performed correctly and take advantage of the fact the new id is the correct data type for joins to other tables using NEW_ID