schema changes

schema/create-schema.sql

@@ -33,10 +33,6 @@ insert into sensor_t (address, label, index, device)
          (10664523975231507496, '3,0m ', 2, 1), 
          (15276209993662477608, '4,0m ', 3, 1);
 
-select d.label as device_label,
-       s.label as label,
-       s.address as address,
-       s.index as index
-  from device_t d, sensor_t s
-  where d.id = s.device;
-  
+create user preprocessor password 'geheim';
+grant select on device_t, sensor_t to preprocessor;
+grant insert on measurement_t to preprocessor;