sql query seems to return no result - mysql

Question

Certain queries that work fine in the mysql command line client don't seem to return
anything at all (no error, no result) in phpMyAdmin.
I get the impression it's related to nested queries.
Here's an example:
select * from
(select
(select min(data) from census2 where
census2.monkey=samplecollection.monkeyid and
date(collectiontime)=date(census2.timestamp)) census
from samplecollection,biograph,hormone,plate
where plate.hormone='Testosterone' and hormone.plateid=plate.plateid and
not specialcontentcode like '%UR%' and thermos!='F' and
biograph.id=monkeyid and samplecollection.sampleid=hormone.sampleid)
t1 limit 3;
+--------+
| census |
+--------+
| GFF |
| GRF |
| GRF |
+--------+
3 rows in set (5.09 sec)
If I extract the inner query (and put the limit on it) then I get a result.

Answer 1

The structure of your query if too complex and clearly not optimized and it may cause the problem you've releved.
Here is the same query with a bit of refactoring:
SELECT *
FROM samplecollection SC
INNER JOIN (SELECT C2.monkeyid
,MIN(C2.data) AS [census]
FROM census2 C2
INNER JOIN samplecollection SC2 ON SC2.monkeyid = C2.monkey
AND DATE(SC2.collectiontime) = DATE(C2.timestamp)
AND SC2.thermos != 'F'
AND SC2.specialcontentcode NOT LIKE '%UR%'
GROUP BY C2.monkeyid) T ON T.monkeyid = SC.monkeyid
INNER JOIN biograph B ON B.id = SC.monkeyid
INNER JOIN hormone H ON H.sampleid = SC.sampleid
INNER JOIN plate P ON P.plateid = H.plateid
AND P.hormone = 'Testosterone'
LIMIT 3
The answer comes late but it may be useful for some people to see how some very complex query structures can be simplified when using JOIN clauses.
Hope this will help.