Mysql - Improving consultation query in 'group by' - sql

Question

I have a query with 'group by':
SELECT date_audience,
Sum( If( quality_apuration = '1', 1, 0 ) ) AS very_good,
Sum( If( quality_apuration = '2', 1, 0 ) ) AS good,
Sum( If( quality_apuration = '3', 1, 0 ) ) AS bad,
Sum( If( quality_apuration = '4', 1, 0 ) ) AS no_apuration,
Count(quality_apuration) AS total
FROM pp_base
WHERE date_audience >= '2011-01-01' AND date_audience <= '2011-02-28'
GROUP BY date_audience ORDER BY date_audience ASC
Where to return the following result (or see http://jsbin.com/imuru5/):
As the table X has foreign key to another table Y, eventually someone will ask to include one more item in the table Y, for example: 'exccelent', 'regular', etc. And I will also have to adjust the schedule as php $query[0]['very_good'], $query[0]['good'], $query[0]['bad'], etc, adding among other items, spending more time .
Does anyone have any idea how I can improve this query, in order to automate the results?
Thanks, Vinicius.

Answer 1

I can see two options.
1) Dealing with it in the application. The following query will perform neccesary aggregation in the database and return 4 rows for each date_audience (one for each value of quality_apuration).
select date_audience
,quality_apuration
,count(*)
from pp_base
where date_audience >= date '2011-01-01'
and date_audience <= date '2011-02-28'
group
by date_audience
,quality_apuration
order
by date_audience
,quality_apuration;
This is preferred when you expect changes to the quality_apuration values.
2) Dealing with it in the database. You could define a view like the following:
create or replace view pp_view as
select date_audience
,sum(case when quality_apuration = '1' then 1 else 0 end) as very_good
,sum(case when quality_apuration = '2' then 1 else 0 end) as good
,sum(case when quality_apuration = '3' then 1 else 0 end) as bad
,sum(case when quality_apuration = '4' then 1 else 0 end) as no_apuration
,count(quality_apuration) as total
from pp_base
group
by date_audience;
...from the application you would then select as follows:
select ...
from pp_view
where date_audience >= date '2011-01-01'
and date_audience <= date '2011-02-28'
order
by date_audience;
Of course, whenever you add another value for quality_apuration, you would have to modify the view definition. Still, it's better than modifying all queries.