PL/SQL Procedure to update values

PL/SQL Procedure to update values in a table based on values taken from another table.

EXAMPLE :
SQL> desc change_log

Name Null? Type
----------------------------------------- -------- ----------------------------
LOG_ID NOT NULL NUMBER(11)
POLL_ID NOT NULL NUMBER(11)
QUESTION_ID NOT NULL NUMBER(11)
ANSWER_ID NOT NULL NUMBER(11)
COUNT NOT NULL NUMBER(11)
TIME NOT NULL DATE

SQL> desc answers

Name Null? Type
----------------------------------------- -------- ----------------------------
ANSWER_ID NOT NULL NUMBER(11)
QUESTION_ID NOT NULL NUMBER(11)
POLL_ID NOT NULL NUMBER(11)
ANSWER_TEXT NOT NULL VARCHAR2(512)
ANSWER_VOTES NOT NULL NUMBER(11)

## Update answers table based on certain conditons on the change_log table.

EXECUTE DBMS_SESSION.SET_NLS('NLS_DATE_FORMAT','''DD-MON-YYYY HH24:MI:SS''');
SET SERVEROUTPUT ON;
execute dbms_output.enable(1000000000);

Declare
Begin
for rec in (
select sum(NVL(change_log.count,0)) as count_total , POLL_ID,QUESTION_ID,ANSWER_ID
from change_log
group by POLL_ID,QUESTION_ID,ANSWER_ID
)
LOOP
begin
update answers
set answers.ANSWER_VOTES= NVL(rec.count_total,0)
where answers.ANSWER_ID=rec.ANSWER_ID
and answers.QUESTION_ID=rec.QUESTION_ID
and answers.POLL_ID=rec.POLL_ID
and answers.answer_id=3;
exception when Others then
dbms_output.put_line ( rec.ANSWER_ID || ' - ' ||rec.ANSWER_ID||' - '||rec.POLL_ID);
end;
END LOOP;
End;
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