Trying to bring back records with and without email address

Question

I have a simple query where I am trying to pull back all of my active subscribers and their email addresses. Most of the subscribers do not have email address but I still want those subscribers in my results. I figure it is a simple join but I can not figure it out. The discus.ems table contains only email addresses and their corresponding RRN's(Acct#'s). The SQL is pasted below. I am using SQL Developer 1.5.5
select
a.STREET_NBR ||' '||
rtrim(substr(a.STREET,33,2)) ||' '||
rtrim(substr(a.STREET,1,28)) ||' '||
rtrim(substr(a.STREET,29,4)) ||' '||
rtrim(substr(a.STREET,35,2)) ADDRESS1,
trim(a.UNIT_NBR) APT,
a.CITY_NAME CITY,
a.STPV_CODE STATE,
a.ZIP_CODE ZIP,
b.email_addr
from
discus.sub a,
discus.ems b
where
a.siteid = 'SUN' and
b.siteid = 'SUN' and
a.rrn = b.sub_rrn and
a.stat_flag in ('E','C','I','V')

Answer 1

For just one column, you could easily do a scalar subquery:
select a.STREET_NBR ||' '||
       rtrim(substr(a.STREET,33,2)) ||' '||
       rtrim(substr(a.STREET,1,28)) ||' '||
       rtrim(substr(a.STREET,29,4)) ||' '||
       rtrim(substr(a.STREET,35,2)) ADDRESS1,
       trim(a.UNIT_NBR) APT,
       a.CITY_NAME CITY,
       a.STPV_CODE STATE,
       a.ZIP_CODE ZIP,
       (select b.email_addr
        from   ems b
        where  b.sub_rrn = a.rrn
        and    b.siteid = 'SUN'
       ) email
from   sub a
where  a.siteid = 'SUN'
and    a.stat_flag in ('E','C','I','V')
;