SELECT TF2_PUBID,TZ_DD,ISNULL(DATEDIFF(MINUTE, TZ_DD2, TZ_DD), 0)
FROM ( SELECT TF2_PUBID,
TZ_DD ,
( SELECT TOP 1
TZ_DD
FROM tablename t2
WHERE t2.TZ_DD < tablename.TZ_DD AND t2.TF2_PUBID=tablename.TF2_PUBID
ORDER BY rq DESC
) AS TZ_DD2
FROM tablename
) temp