I've got a little issue. I've got to do a query that is based on a subquery.
The SQL query I need to get to is:
FROM testing t
WHERE t.id NOT IN (
SELECT h.task_id
FROM task t
INNER JOIN hardware h ON h.task_id = t.id
);
What I have for a moment is the basic query and I don't really understand how to do that subquery..
$test->createQueryBuilder('t')
->select('t.id')
->getQuery()->getArrayResult();
Related
I am trying to compare values against same table which has more than 1,000,000 rows. Below is my query and it takes around 25 secs to get results.
EXPLAIN SELECT DISTINCT a.studyid,a.number,a.load_number,b.studyid,b.number,b.load_number FROM
(SELECT t1.*, buildnumber,platformid FROM t t1
INNER JOIN testlog t2 ON t1.`testid` = t2.`testid`
WHERE (buildnumber =1031719 AND platformid IN (SELECT platformid FROM platform WHERE platform.`Description` = "Windows 7 SP1"))
)AS a
JOIN
(SELECT t1.*,buildnumber,platformid FROM t t1
INNER JOIN testlog t2 ON t1.`testid` = t2.`testid`
WHERE (buildnumber =1030716 AND platformid IN (SELECT platformid FROM platform WHERE platform.`Description` = "Windows 7 SP1"))
)AS b
ON a.studyid=b.studyid AND a.load_number = b.load_number AND a.number = b.number
Could you anyone help me to improve this query to get fast enough results?
The problem here is even I have number and load_number index, the query doesn't use that. I dont know why it is always ignored..
Thanks.
First, you have a silly query. You are retrieving six columns, but there are only three values. Look at the on clause.
I think your best bet is to rewrite the query using conditional aggregation. I think the following is equivalent:
SELECT t1.studyid, t1.load_number, t1.number
FROM t t1 INNER JOIN
testlog t2
ON t1.testid = t2.testid
WHERE t2.buildnumber IN (1031719, 1030716) AND
platformid IN (SELECT platformid FROM platform p WHERE p.Description = 'Windows 7 SP1'))
GROUP BY studyid, load_number, number
HAVING MIN(buildnumber) <> MAX(buildnumber)
For this query, you want indexes on platform(Description, platformid) and testlog(buildnumber, platformid) and t(testid).
Problem #1:
IN ( SELECT ... ) optimizes very poorly. The subquery is rerun again and again. It looks like you are expecting exactly one id from that query; if so, change it to = ( SELECT ... ). That way it will be run exactly once.
Problem #2:
FROM ( SELECT ... )
JOIN ( SELECT ... ) ON ...
optimizes poorly because neither subquery. Can you merge the two subqueries into one, as Gordon was trying? If not, then put one of them into a TEMPORARY TABLE and add an appropriate index to that table so that the ON will be able to use it. Probably PRIMARY KEY(studyid, load_number, number).
Footnote: The latest versions of MySQL have made improvements on these problems by dynamically generating indexes. What version are you using?
I have the following query:
SELECT PKID, QuestionText, Type
FROM Questions
WHERE PKID IN (
SELECT FirstQuestion
FROM Batch
WHERE BatchNumber IN (
SELECT BatchNumber
FROM User
WHERE RandomString = '$key'
)
)
I've heard that sub-queries are inefficient and that joins are preferred. I can't find anything explaining how to convert a 3+ tier sub-query to join notation, however, and can't get my head around it.
Can anyone explain how to do it?
SELECT DISTINCT a.*
FROM Questions a
INNER JOIN Batch b
ON a.PKID = b.FirstQuestion
INNER JOIN User c
ON b.BatchNumber = c.BatchNumber
WHERE c.RandomString = '$key'
The reason why DISTINCT was specified is because there might be rows that matches to multiple rows on the other tables causing duplicate record on the result. But since you are only interested on records on table Questions, a DISTINCT keyword will suffice.
To further gain more knowledge about joins, kindly visit the link below:
Visual Representation of SQL Joins
Try :
SELECT q.PKID, q.QuestionText, q.Type
FROM Questions q
INNER JOIN Batch b ON q.PKID = b.FirstQuestion
INNER JOIN User u ON u.BatchNumber = q.BatchNumber
WHERE u.RandomString = '$key'
select
q.pkid,
q.questiontext,
q.type
from user u
join batch b
on u.batchnumber = b.batchnumber
join questions q
on b.firstquestion = q.pkid
where u.randomstring = '$key'
Since your WHERE clause filters on the USER table, start with that in the FROM clause. Next, apply your joins backwards.
In order to do this correctly, you need distinct in the subquery. Otherwise, you might multiply rows in the join version:
SELECT q.PKID, q.QuestionText, q.Type
FROM Questions q join
(select distinct FirstQuestion
from Batch b join user u
on b.batchnumber = u.batchnumber and
u.RandomString = '$key'
) fq
on q.pkid = fq.FirstQuestion
As to whether the in or join version is better . . . that depends. In some cases, particularly if the fields are indexed, the in version might be fine.
I am trying to optimize this query:
SELECT ob.id, obs.relation
FROM object_relation obs , object_table ob
WHERE obs.parent_id = 'ID_being_passed_as_parameter'
AND ob.id = obs.child_id
AND ob.deleted_object_flag=0
AND ob.id_prefix in ('prefix_variAble_passed')
ORDER BY (SELECT m.value FROM metadata_table
m WHERE ob.version_id=m.version_id AND m.name='SORTING_CONDITION' )
Is is possible to optimize it?
Any suggestions would be of great help
Your query sucks because it's executing the subquery in the order by for every row.
Most subqueries can be turned into joins. This is what you should do too, as well as use joins in your main query:
SELECT ob.id, obs.relation
FROM object_relation obs
join object_table ob
on ob.id = obs.child_id
AND ob.deleted_object_flag=0
AND ob.id_prefix in ('prefix_variable_passed')
left join metadata_table m
on ob.version_id = m.version_id
AND m.name = 'SORTING_CONDITION'
WHERE obs.parent_id = 'ID_being_passed_as_parameter'
ORDER BY m.value;
This use of left join allows for there to be no matching row in metadata_table but still appear in the results.
Note also moving the predicates into the on clause of the join where they can be applied as the row is joined rather than at the end, which is much more efficient as the temporary result set is as small as possible.
I really need help here, does anyone know how to transform this SQL query into a Doctrine2 query using the createQueryBuilder?
SELECT a.resposta,
(
SELECT count(r.id)
FROM car_resultado r2
LEFT JOIN car_resultado_inquerito ri2 ON r2.id_resultado_inquerito = ri2.id
WHERE ri2.id_inquerito = 20 AND r2.id_resposta = a.id
GROUP BY r2.id_pergunta, r2.id_resposta
) as total
FROM car_resposta a
LEFT JOIN car_resultado r ON ( r.id_resposta = a.id )
GROUP BY a.id, r.id_resposta
I have no idea how to do it, mainly because that nested SELECT
Normally you have to create your Entities and Repositories to get the data from your database. But in Doctrine2 is a uncool way. You can execute native SQL.
Doctrine2 Native SQL
If its possible you shouldn't do it and work with the classes but if you have a complicated existing queries you can do it.
I have a bulk query with subquery. My query works fine when I run it on development server, but when I've try it pn the live server, the query takes too much time to produce an output. I think it's because of a big data on the live server. Can anyone help me on how to index query on MySQL so that it will lessen the time execution.
Here is my query:
SELECT prd.fldemployeeno AS Empno,
(SELECT fldemployeename FROM tblprofile prf WHERE prf.fldemployeeno = prd.fldemployeeno LIMIT 0,1) AS Empname,
'01' AS `Week`,
COUNT(DISTINCT isAud.fldid) AuditedFiles,
COUNT(qua.seqid) ErrorCount,
COUNT(DISTINCT qua.fldid) OrdersWithError
FROM tbldownloadITL dwn
INNER JOIN tblproductionITL prd
ON dwn.fldid = prd.fldglobalid
INNER JOIN (SELECT p.fldemployeeno,fldglobalid,p.fldstarttime,COALESCE(q.fldstarttime,p.fldstarttime) `AuditDate`
FROM tblproductionitl p
LEFT JOIN tblqualityaudit q
ON p.fldemployeeno=q.fldemployeeno
AND p.fldstarttime=q.fldprodstarttime
AND p.fldglobalid=q.fldid
WHERE p.fldprojectgroup='PROJGROUP') temp
ON prd.fldglobalid=temp.fldglobalid
AND prd.fldemployeeno=temp.fldemployeeno
AND prd.fldstarttime=temp.fldstarttime
INNER JOIN tblisauditedITL isAud
USING (fldid)
LEFT JOIN tblqualityaudit qua
ON qua.fldid = dwn.fldid
AND qua.fldbusunit = dwn.fldbusunit
AND qua.fldprojectGroup = dwn.fldprojectGroup
AND qua.fldemployeeno = prd.fldemployeeno
AND qua.fldprodstarttime = prd.fldstarttime
AND qua.flderrorstatus != 'NOT ERROR'
LEFT JOIN tblerrorcategory
USING (flderrorcategoryid)
LEFT JOIN tblerrortypes
USING (flderrortypeid)
WHERE dwn.fldbusunit = 'BUSUNIT'
AND dwn.fldprojectGroup = 'PROJGROUP'
AND temp.AuditDate BETWEEN '2011-07-29 00:00:00' AND '2011-07-29 23:59:59'
GROUP BY prd.fldemployeeno
ORDER BY Empname
Here is also the description of the query:
I would suggest installing Sphinx on the your server if you have the access. That way you can have an indexed resource at your finger tips for extremely fast searching, on top of that you can add the execution of what is called a 'delta' index to allow for real time updating of your mysql database. It is highly customizable. Hopefully this will help you out.
http://sphinxsearch.com/