mysql - select distinct mutually exclusive (based on another column's value) rows - mysql

Question

First off, I would like to say that if after reading the question, anyone has a suggestion on a more informative title for this question, please tell me, as I think mine is somewhat lacking, now, on to business...
Given this table structure:
+---------+-------------------------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------+-------------------------------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| account | varchar(20) | YES | UNI | NULL | |
| domain | varchar(100) | YES | | NULL | |
| status | enum('FAILED','PENDING','COMPLETE') | YES | | NULL | |
+---------+-------------------------------------+------+-----+---------+----------------+
And this data:
+----+---------+------------------+----------+
| id | account | domain | status |
+----+---------+------------------+----------+
| 1 | jim | somedomain.com | COMPLETE |
| 2 | bob | somedomain.com | COMPLETE |
| 3 | joe | somedomain.com | COMPLETE |
| 4 | frank | otherdomain.com | COMPLETE |
| 5 | betty | otherdomain.com | PENDING |
| 6 | shirley | otherdomain.com | FAILED |
| 7 | tom | thirddomain.com | FAILED |
| 8 | lou | fourthdomain.com | COMPLETE |
+----+---------+------------------+----------+
I would like to select all domains which have a 'COMPLETE' status for all accounts (rows).
Any domains which have a row containing any value other then 'COMPLETE' for the status must not be returned.
So in the above example, My expected result would be:
+------------------+
| domain |
+------------------+
| somedomain.com |
| fourthdomain.com |
+------------------+
Obviously, I can achieve this by using a sub-query such as:
mysql> select distinct domain from test_table where status = 'complete' and domain not in (select distinct domain from test_table where status != 'complete');
+------------------+
| domain |
+------------------+
| somedomain.com |
| fourthdomain.com |
+------------------+
2 rows in set (0.00 sec)
This will work fine on our little mock-up test table, but in the real situation, the tables in question will be tens (or even hundreds) of thousands of rows, and I'm curious if there is some more efficient way to do this, as the sub-query is slow and intensive.

Answer 1

How about this:
select domain
from test_table
group by domain
having sum(case when status = 'COMPLETE'
then 0 else 1 end) = 0

Answer 2

I think this will work. Effectively just joins two basic queries together, then compares their count.
select
main.domain
from
your_table main
inner join
(
select
domain, count(id) as cnt
from
your_table
where
status = 'complete'
group by
domain
) complete
on complete.domain = main.domain
group by
main.domain
having
count(main.id) = complete.cnt
You should also ensure you have an index on domain as this relies on a join on that column.