I think you will need a further query which returned the max(txtnr) for each jobnr which would be used as further where-clause. Perhaps as in front query or in a nested query.
Maybe it could be an alternatively to load the sql raw-data tables directly in qv and make such transforming or filtering steps within qv.
You may load the entire table into QlikView and then reload/restrict the data by using FIRSTSORTEDVALUE-function.
This is advisable, if you are looking for two or three output-fields only.
You may join the entire-table with the max-value and then apply a filter:
LEFT JOIN (Table1) LOAD
MAX(TxtNr) AS TxtNr
'I am the Last entry' AS FilterMe
NOCONCATENATE LOAD * RESIDENT Table1 WHERE FilterMe = 'I am the Last Entry';
DROP TABLE Table1;