Parent-child sql query with order by and limit - sql

Question

I have two tables DOCUMENT and ATTRIBUTES like these
DOCUMENT(id),
ATTRIBUTE(name, value, doc_fk).
I need to run a query that works like this "abstract query"
select top 100 documents
where $state='COMPLETED'
order by $creationDate
Where $state and $creationDate are two attributes.
Note that the limit is on documents, not attributes, and sort and filter are on two different attributes. The final query should return all document attributes, not only the filtered/sorted ones.
I was able to write this with a very complex query and I'm looking for better alternatives. I could post my solution if useful, but I do not want to point you in the, possibly, wrong direction.
It's ok to get a FEW extra documents, like 1000 instead of 100, and filter/sort in memory.
Could be ok for the limit not to be exact, like 74 instead of the required limit 100, but not too far from it.
Extra "soft" requirements:
the query should work with several databases (oracle, mysql and sqlserver), so weird analytic functions should be avoided unless available on all platforms
should work with JPA (eclipselink 2.4.0 implementation)
The expected output is something like this
DOC_ID ATTRIBUTE_NAME VALUE
123 state COMPLETED
123 creationDate 21/11/2012
123 userid someone
456 state COMPLETED
...

Answer 1

Ah, the flaws of an EAV design.
Try this.
select
top 100
document.*
from document
inner join attribute astate on document.id = astate.doc_fk
and astate.name='state'
and astate.value = 'completed'
inner join attribute acreation on document.id = acreation.doc_fk
and acreation.name='creationdate'
order by cast(acreation.value as date)
But it's only going to get more complicated if you persist with this EAV structure.
(PS. MySQL doesn't use TOP, but LIMIT instead)

Answer 2

SELECT doc_id, attr_name, attr_val, creationDate FROM
(
SELECT * FROM (
SELECT
doc.id as 'doc_id', attr.name as 'attr_name', null as 'attr_val', attr.value as 'creationDate'
FROM
ATTRIBUTE attr
LEFT JOIN
DOCUMENT doc ON attr.doc_fk = doc.id
WHERE
attr.name='creationDate'
ORDER BY creationDate desc;
) AS dt1
UNION ALL
SELECT * FROM(
SELECT
doc.id as 'doc_id', attr.name as 'attr_name', attr.value as 'attr_val', null as 'creationDate'
FROM
ATTRIBUTE attr
LEFT JOIN
DOCUMENT doc ON attr.doc_fk = doc.id;
) as dt2
) as dt0 GROUP BY doc_id ORDER by creationDate desc LIMIT 100;
Derived table 1 (dt1) gives you all the date attributes - to enable order your results by document's creation date.
Derived table 2 gives you all the attribute.. all put together by "union all", enables you to group by document, then order by the date of creation.
Hope this is in the right direction.