Hello Carlo
In Bacula communiy is not possible yet (maybe in Enterprise version only)
Probably in the Schedule you have more than one Level for this job.
You could adapt you script for receive a parameter like "Level" from Job and in the script select the the Full or Incremental using the value of parameter passed
Job {
Name = "Backup_XXX"
...
RunBeforeJob = "/etc/bacula/scripts/backup_database.sh %l" # %l = Job Level
...
}