summary view design / performance

Morning all,

I'm after people's opinions redarding performance / system load in the
following select / view. Also, if there is a better technique I'd love to
hear it.

I have the following table, which is an audit and message log for amendments
to the service_jobs table.

Table "public.service_jobs_log"
Column | Type |
Modifiers
---------------+-----------------------------+-------------------------------------------------------------------
sj_seq | integer | not null default
nextval('service_jobs_log_sj_seq_seq'::regclass)
sj_id | integer | not null
sj_u_id | integer | not null
sj_text | text | not null
sj_timestamp | timestamp without time zone | default now()
sjl_id | integer | not null default 10
sjl_answer_to | integer |
Indexes:
"service_jobs_log_pkey" PRIMARY KEY, btree (sj_seq)
"service_jobs_log_sj_id_index" btree (sj_id)
"service_jobs_log_sj_timestamp_index" btree (sj_timestamp)
"service_jobs_log_sjl_id_index" btree (sjl_id)
Foreign-key constraints:
"service_jobs_log_sj_id_fkey" FOREIGN KEY (sj_id) REFERENCES
service_jobs(sj_id)
"service_jobs_log_sj_u_id_fkey" FOREIGN KEY (sj_u_id) REFERENCES
users(u_id)
"service_jobs_log_sjl_answer_to_fkey" FOREIGN KEY (sjl_answer_to)
REFERENCES service_jobs_log(sj_seq)
"service_jobs_log_sjl_id_fkey" FOREIGN KEY (sjl_id) REFERENCES
service_jobs_log_types(sjl_id)

goole=# select * from service_jobs_log_types order by sjl_id;
sjl_id | sjl_desc | sjl_show_chat | sjl_colour
--------+----------+---------------+------------
10 | Activity | f |
20 | Comment | f |
30 | Question | f |
40 | Answer | f |
(4 rows)

The view I want is:

j_id
count
comment_count
highest_comment_seq
question_count
highest_question_seq
answer_count
highest_answer_seq

I have two solutions. Firstly having multiple sub-selects

select sjl.sj_id, sjl.count,
coalesce(cc.count,0) as comment_count, cc.max as highest_comment_seq,
coalesce(qc.count,0) as question_count, qc.max as highest_question_seq,
coalesce(ac.count,0) as answer_count, ac.max as highest_answer_seq
from (select sj_id, count(sj_id) from service_jobs_log group by sj_id) sjl
left outer join (select sj_id, count(sj_id), max(sj_seq) from
service_jobs_log where sjl_id=20 group by sj_id) cc on sjl.sj_id = cc.sj_id
left outer join (select sj_id, count(sj_id), max(sj_seq) from
service_jobs_log where sjl_id=30 group by sj_id) qc on sjl.sj_id = qc.sj_id
left outer join (select sj_id, count(sj_id), max(sj_seq) from
service_jobs_log where sjl_id=40 group by sj_id) ac on sjl.sj_id = ac.sj_id
;
Secondly, having one query with lots of case statements

select sj_id, count(sj_id),
count(comments) as comment_count, max(comment_seq) as highest_comment_seq,
count(questions) as question_count, max(question_seq) as
highest_question_seq,
count(answers) as answer_count, max(answer_seq) as highest_answer_seq
from (
select sj_id,
case when sjl_id = 20 then 1 else NULL end as comments,
case when sjl_id = 20 then sj_seq else NULL end as comment_seq,
case when sjl_id = 30 then 1 else NULL end as questions,
case when sjl_id = 30 then sj_seq else NULL end as question_seq,
case when sjl_id = 40 then 1 else NULL end as answers,
case when sjl_id = 40 then sj_seq else NULL end as answer_seq
from service_jobs_log) foo
group by sj_id;

In the production environment the view will be called with a list of required
sj_id's, e.g.

select * from service_job_log_summary where sj_id in (123,124,145..........)