gistfile1.txt

SELECT
    total.count,
    detail.basetag,
    detail.alarms_id
FROM
    (
        SELECT
            basetag,
            count(*)
        FROM
            alarms
        GROUP BY basetag
        ORDER BY
            count DESC,
            basetag ASC
    ) as total
JOIN
    (
        SELECT *,
            row_number() OVER (PARTITION BY basetag ORDER BY firstoccurence ASC, alarms_id ASC)
        FROM
            alarms
    ) AS detail ON detail.basetag = total.basetag
WHERE row_number = 1