Oracle 21c

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CREATE TABLE MyTable(col1, col2) AS
SELECT 1, 'Val1' FROM DUAL UNION ALL
SELECT 2, 'Val2' FROM DUAL UNION ALL
SELECT 3, 'Val3' FROM DUAL UNION ALL
SELECT 4, 'Val4' FROM DUAL;
4 rows affected

SELECT Col2
FROM   MyTable A
WHERE  Col1 IN (2,3,4)


COL2


Val2

Val3

Val4


SELECT Col2,
       (SELECT LISTAGG(col1, ',') WITHIN GROUP (ORDER BY col1)
        FROM   MyTable B
        WHERE  B.Col1 = A.Col1) AS equal,
       (SELECT LISTAGG(col1, ',') WITHIN GROUP (ORDER BY col1)
        FROM   MyTable B
        WHERE  B.Col1 <> A.Col1) AS not_equal
FROM   MyTable A
WHERE  Col1 IN (2,3,4)


COL2
EQUAL
NOT_EQUAL


Val2
2
1,3,4

Val3
3
1,2,4

Val4
4
1,2,3


SELECT Col2
FROM   MyTable A
WHERE  Col1 IN (2,3,4)
AND    NOT EXISTS(
         SELECT 1
         FROM MyTable B
         WHERE B.Col1 <> A.Col1
       )