need help to write a function in postgresql

Hi Friends

Can u please help to write a function for the following scenario?

I have 3 table's user_roles, principals and roles.

I have to write a function in postgresql which should excepts 2 parameters
(name, password)

With those 2 parameters the query should be executed and return the
result.(Result of the query will be 1 or more rows).

The query is working fine if executed it manually by hardcoding the values
for name and password, but is as to be written in function so that I can
send different values.

"select
u.role_id,u.user_id,p.name,p.creation_date,p.telephone_number,p.email,p.rema
rks,p.city,p.state,p.country,p.postal_address,p.company_name,p.department_na
me,p.contact_person,

p.role_group,p.role_description,p.first_name,p.last_name,p.pincode,p.status,
p.department_id,p.designation_id,r.role_name,r.right_edit,r.right_filter,r.r
ight_search,r.right_browse,

r.right_print,
r.right_download,r.right_admin_user,r.right_image_creator,r.right_vector_dow
nload,r.right_wps,r.right_queries_filter,r.right_google_map,r.right_user_man
agement,

r.right_route_analysis,
r.right_legend,r.right_treeview,r.insert,r.update,r.delete,r.query,r.lock
from user_roles u,.principals p,roles r where p.PRINCIPAL_ID = u.USER_ID and

r.role_id = u.role_id and p.name=? and p.password=?"

Thanks in Advance.

Regards

Madhu.Lanka