Update using having and MIN function non key-preserved table error - sql

Question

I have below data in two different tables. I am able to retrieve required records using select query, however I am unable to update ROW_IND of these records. The update statement I used gives me error. Any pointers will be much appreciated.
Table CLP :
ID KEY EFF_DT ROW_IND
28420000000006 4599 1/1/2000 1
28420000000006 21164 10/16/2019 1
28420000000011 58429 1/1/2000 1
28420000000011 68434 10/16/2019 1
Table CPI :
KEY2 ID2
21164 28420000000006
68434 28420000000011
The Query :
SELECT p.id , p.key, i.key AS KEY2, i.id AS ID2, p.EFF_DT, p.row_ind
FROM CLP P, CLI I
WHERE p.id = i.id
AND P.KEY <> I.KEY
AND p.row_ind = 1
AND P.id IN
(
SELECT id
FROM CLP
WHERE row_ind = 1
GROUP BY id
HAVING count(*) > 1
);
ID KEY KEY2 ID2 EFF_DT ROW_IND
28420000000006 4599 21164 28420000000006 1/1/2000 1
28420000000011 58429 68434 28420000000011 1/1/2000 1
The Update Query:
UPDATE
(
< The Above SELECT Query >
) A
SET A.row_ind = 0
Error: ORA-01779: cannot modify a column which maps to a non key-preserved table

Answer 1

This syntax for an UPDATE statement cannot be used within Oracle while might be used within MySQL. Alternatively, you can try to use a MERGE statement :
MERGE INTO CLP t
USING
(
SELECT p.id , p.key, i.key AS KEY2, i.id AS ID2, p.EFF_DT, p.row_ind
FROM CLP p
JOIN CPI i
ON p.id = i.id
WHERE p.key <> i.key
AND p.row_ind = 1
AND P.id in
(
SELECT id
FROM CLP
WHERE row_ind = p.row_ind
GROUP BY id
HAVING count(*) > 1
)
) tt
ON (tt.key2 = t.key)
WHEN MATCHED THEN UPDATE SET t.row_ind = 0;
where
you'd better converting the old-style SELECT statement to the
syntax containing explicit JOIN keywords instead of comma-seperated
JOINs
no need to repeat the condition row_ind = 1 twice, replacing the
second one with row_ind = p.row_ind is more preferable
Demo