Corion suggest that i could have the script (pquota) called another one (mypquota).
but the difference is that

pquota is 0755 lp staff
mypquota 0700 lp lp

then i can have the database user name and password in the mypquota scirpt that no once will see except lp group and user. that seems to be the easiest way, i guess.