'How to select non "unique" rows

I have the following table, from which i have to fetch non unique rows

I'd like fetch all the rows for the column infos, that have a same idA value in at least two rows.

Output of the query for the above table must be

infos
1899
1959

I've tried the following requests with no success :

SELECT idA FROM XXX WHERE NOT EXISTS(SELECT * FROM XXX GROUP BY idA)
SELECT * FROM XXX a WHERE NOT EXISTS(SELECT * FROM XXX b WHERE a.RVT_ID=b.RVT_ID GROUP BY idA)

mysql sql

Solution 1:^[1]

Try this:

SELECT T1.idA, T1.infos
FROM XXX T1
JOIN
(
    SELECT idA
    FROM XXX
    GROUP BY idA
    HAVING COUNT(*) >= 2
) T2
ON T1.idA = T2.idA

The result for the data you posted:

idaA  infos
201   1899
201   1959

Something like this should work:

SELECT idA, COUNT(*) FROM XXX GROUP BY idA HAVING COUNT(*) > 1

SELECT id, idA, COUNT(infos) AS cnt
FROM mytable
GROUP BY infos
HAVING cnt > 1

This is probably what you are looking for:

SELECT *, COUNT(DISTINCT infos) FROM table GROUP BY idA HAVING COUNT(DISTINCT infos) > 1;

This should give all the rows where "infos" appear exactly once (Tested on MySQL)

SELECT id, idA, count(infos) AS cnt
FROM mytable
GROUP BY infos
HAVING cnt=1

Data

id  ida     infos
1   201     1955
2   202     1978
3   203     1978
4   204     1956
5   0   1980

Result

id  idA     cnt
1   201     1
4   204     1
5   0   1

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