sql - 在另一列中选择具有相同ID但不同值的行

Question

Input:

Column A	Column B
1	A
1	B
1	C
2	A
2	B
3	A
3	B
3	c
4	A
5	A
5	B
6	A

Output

ColumnA
4
6.

for columnA for every first of values is A, i need to fetch columnA those values have only A not in B,C

Answer 1

You can use a correlated subquery with NOT EXISTS to exclude column A values that have matching rows with the disallowed values in column B.

SELECT columnA
FROM yourTable AS t1
WHERE columnB = 'A'
AND NOT EXISTS (
    SELECT *
    FROM yourTable AS t2
    WHERE t1.columnA = t2.columnA
        AND t2.columnB IN ('B', 'C')
)