slow query with joins - mysql

Please am having difficulty in optimizing this query. What am trying to achieve is to join about 8 tables, of which only about 3 of the tables contains large data (1.5m records). This query returns expected records but is taking 1min to run which is bad.
I know it can be optimized to perform far better, pls i need assistance from you experts. I have index on the fields used for join already.
SELECT topic_id,
topic_title,
unit_name_abbrev,
sch_name_abbrev,
picture_small_url AS thumbnail,
profile_pix_upload_path,
first_name,
last_name,
topic_poster,
topic_replies,
topic_views,
topic_last_post_time AS topic_post_time,
sch_sub_forum_id
FROM (_sch_forum_topics
INNER JOIN _users
ON ( _users.userid = _sch_forum_topics.topic_poster )
INNER JOIN _profile
ON _profile.userid = _users.userid
INNER JOIN _class
ON _users.classid = _class.classid
INNER JOIN _level
ON _class.level_id = _level.id
INNER JOIN _unit
ON _class.unitid = _unit.unitid
INNER JOIN _department
ON _unit.deptid = _department.deptid
INNER JOIN _faculty
ON _department.facid = _faculty.facid
INNER JOIN _university
ON _faculty.schid = _university.schid)
WHERE _sch_forum_topics.sch_sub_forum_id = 4
ORDER BY _sch_forum_topics.topic_last_post_time DESC
LIMIT 0, 15

Try to filter before making JOIN's.
SELECT topic_id,
topic_title,
unit_name_abbrev,
sch_name_abbrev,
picture_small_url AS thumbnail,
profile_pix_upload_path,
first_name,
last_name,
topic_poster,
topic_replies,
topic_views,
topic_last_post_time AS topic_post_time,
sch_sub_forum_id
FROM
( select * FROM sch_forum_topics WHERE sch_sub_forum_id = 4
ORDER BY topic_last_post_time DESC
LIMIT 0, 15 ) main
INNER JOIN _users
ON ( _users.userid = main.topic_poster )
INNER JOIN _profile
ON _profile.userid = _users.userid
INNER JOIN _class
ON _users.classid = _class.classid
INNER JOIN _level
ON _class.level_id = _level.id
INNER JOIN _unit
ON _class.unitid = _unit.unitid
INNER JOIN _department
ON _unit.deptid = _department.deptid
INNER JOIN _faculty
ON _department.facid = _faculty.facid
INNER JOIN _university
ON _faculty.schid = _university.schid);

Related

how understand the relation between parent query and subquery in mysql?

Someone please explain the difference between parent query and sub query? How do I understand?
e.g:
SELECT
ra.ID id,
ra.ACCOUNT_ID accountId,
ef.REAL_NAME realName,
a.MOBILE mobile,
sps.`NAME` siteName,
ef.CREATE_TIME createTime,
a.`STATUS` status,
ra.`STATUS` siteStatus,
(
SELECT
aif.APPROVER_NAME
FROM
audit_info aif
WHERE
aif.TARGET_ID = a.ID AND af.AUDIT_TYPE=2
AND aif.CREATE_TIME = (
SELECT
MAX(af.CREATE_TIME)
FROM
audit_info af
WHERE
af.TARGET_ID = a.ID AND af.AUDIT_TYPE=2
)
) AS approverName
FROM
account a
INNER JOIN site_relation_account ra ON ra.ACCOUNT_ID = a.ID
INNER JOIN account_ext ef ON ra.ACCOUNT_ID = ef.ACCOUNT_ID
INNER JOIN service_provider_site sps ON sps.ID = ra.SITE_ID
LEFT JOIN audit_info af ON af.TARGET_ID = ef.ACCOUNT_ID
WHERE ra.ACCOUNT_TYPE = 2

Ho to get last item in mysql using max()

I want to get the last item as result using max(), but i'm just getting the first item even if im using max()
Here's the SQL code:
SELECT r.correct, r.items, r.percentage,MAX(r.date_taken) as date_taken,
u.username,u.FN, u.user_course_type,
IFNULL(u.user_major_type,'N/A') as user_major_type,u.level_name,
u.section_name
FROM bcc_fs_exam_result r
INNER JOIN
(SELECT u.id_user, u.username, CONCAT(u.lastname,', ',u.firstname) as FN,
c.user_course_type, m.user_major_type, l.level_name, s.section_name
FROM bcc_fs_user u
LEFT JOIN bcc_fs_user_course c on c.id_user_course = u.id_user_course
LEFT JOIN bcc_fs_user_major m on m.id_user_major = u.id_user_major
LEFT JOIN bcc_fs_group_level l ON l.id_level = u.id_level
LEFT JOIN bcc_fs_group_section s ON s.id_section = u.id_section
) u ON r.id_user = u.id_user WHERE r.id_exam = 5 GROUP BY r.id_user
TIA
What I take from your question is that you want to get the "correct", "items", "percentage" ect. columns of the row in bcc_fs_exam_result which has the last or first date.
If that's correct then you can filter bcc_fs_exam_result by first finding what is the min or max date by for each id_user then join that back on the exam results table.
SELECT
r.correct,
r.items,
r.percentage,
r.date_taken,
u.username,
u.FN,
u.user_course_type,
IFNULL(u.user_major_type,'N/A') as user_major_type,
u.level_name,
u.section_name
FROM bcc_fs_exam_result r
INNER JOIN (
SELECT u.id_user,
u.username,
CONCAT(u.lastname,', ',u.firstname) as FN,
c.user_course_type,
m.user_major_type,
l.level_name,
s.section_name
FROM bcc_fs_user u
LEFT JOIN bcc_fs_user_course c on c.id_user_course = u.id_user_course
LEFT JOIN bcc_fs_user_major m on m.id_user_major = u.id_user_major
LEFT JOIN bcc_fs_group_level l ON l.id_level = u.id_level
LEFT JOIN bcc_fs_group_section s ON s.id_section = u.id_section
) u ON r.id_user = u.id_user
INNER JOIN (
SELECT
id_user, max(r.date_taken) as last_date_taken
FROM bcc_fs_exam_result
GROUP BY id_user
) as lastdate ON lastDate.id_user = r.id_user and r.date_taken = lastdate.last_date_taken
which could be more simply written as :
SELECT
r.correct,
r.items,
r.percentage,
r.date_taken,
u.username,
CONCAT(u.lastname,', ',u.firstname) as FN,
c.user_course_type,
IFNULL(m.user_major_type,'N/A') as user_major_type,
l.level_name,
s.section_name
FROM bcc_fs_exam_result r
INNER JOIN (
SELECT
id_user, max(r.date_taken) as last_date_taken
FROM bcc_fs_exam_result
GROUP BY id_user
) as lastdate ON lastDate.id_user = r.id_user and r.date_taken = lastdate.last_date_taken
INNER JOIN bcc_fs_user u on r.id_user = u.id_user
LEFT JOIN bcc_fs_user_course c on c.id_user_course = u.id_user_course
LEFT JOIN bcc_fs_user_major m on m.id_user_major = u.id_user_major
LEFT JOIN bcc_fs_group_level l ON l.id_level = u.id_level
LEFT JOIN bcc_fs_group_section s ON s.id_section = u.id_section
You have assumed that id_user + date_taken is a surrogate key of bcc_fs_exam_result which you should probably enforce with a constraint if at all possible. Otherwise it looks from your sample data that the order of the unique id column id_result follows the date_takenso you might be better to use Max(id_result) rather than Max(date_taken). That would avoid returning duplicate rows for one id_user where two rows of bcc_fs_exam_result have the same taken_date and `id_user.

mysql where not in to left outer join

I have the following query and would like to convert it to using a left outer join instead of a not in to see if it would run faster that way. It's currently taking this query about 40 seconds to run on our database. I'm not familiar enough with using outer joins for this type of thing to convert it myself.
select
c.contact_id as contact_id,
c.orgid as organization_id,
c.first_name as first_name,
c.last_name as last_name,
a.address_state as state
from cnx_contact as c
inner join cnx_address as a on c.home_address_uid = a.address_uid
where a.address_state = 'OH'
and (c.orgid = 45 or c.orgid = 55)
and c.contact_id NOT IN (
select pc.contact_id
from cnx_contact as c
inner join cnx_address as a on c.home_address_uid = a.address_uid
inner join cnx_contact_group_participant as gp on c.contact_id = gp.contact_id
inner join cnx_contact_participant_role as cr on gp.participant_role_uid = cr.participant_role_uid
inner join cnx_contact_group as cg on gp.group_uid = cg.group_uid
inner join cnx_contact_group_participant as pgp on cg.primary_participant_uid = pgp.participant_uid
inner join cnx_contact as pc on pgp.contact_id = pc.contact_id
where (c.orgid = 45 or c.orgid = 55)
and cr.name = 'Applicant'
);
select
c.columns
from cnx_contact as c
inner join cnx_address as a on c.home_address_uid = a.address_uid
LEFT JOIN
(Subquery goes here) x
ON x.contact _id = c.contact_id
where a.participant_state = 'OH'
and c.orgid IN(45,55)
and x.contact_id IS NULL;

Speeding up MySQL Query inc subquery-join?

I've got the query below that's pulling data from a number of tables to create an update:
UPDATE en_inter.subscribers_data AS sd
inner join en_inter.list_subscribers AS ls on sd.subscriberid = ls.subscriberid
LEFT JOIN (
SELECT pd1.email_address,COUNT(pd1.email_address) AS NumDowns
FROM email.papr_down pd1
INNER JOIN email.papr_data pd2 on pd1.paper_id = pd2.id
INNER JOIN email.papr_subj ps on ps.id = pd2.subject
INNER JOIN email.papr_exam pe on pe.id = pd2.exam
INNER JOIN email.papr_levl pl on pl.id = pd2.level
WHERE pd2.exam = 1
and pd2.level = 4
GROUP BY email_address
) AS downs ON downs.email_address = ls.emailaddress
SET sd.data = ifnull(downs.NumDowns,1)
WHERE sd.fieldid = 33;
It works fine but when there are plenty of records in papr_down then it takes ages to process. Any ideas about how it can be optimized?
What I think is the join between the emailAddress is the issue here, you can try out with the join with the Id's.
If you provide us the screen shot of the below query ::
EXPLAIN Select * from
en_inter.subscribers_data AS sd
inner join en_inter.list_subscribers AS ls on sd.subscriberid = ls.subscriberid
LEFT JOIN (
SELECT pd1.email_address,COUNT(pd1.email_address) AS NumDowns
FROM email.papr_down pd1
INNER JOIN email.papr_data pd2 on pd1.paper_id = pd2.id
INNER JOIN email.papr_subj ps on ps.id = pd2.subject
INNER JOIN email.papr_exam pe on pe.id = pd2.exam
INNER JOIN email.papr_levl pl on pl.id = pd2.level
WHERE pd2.exam = 1
and pd2.level = 4
GROUP BY email_address
) AS downs ON downs.email_address = ls.emailaddress
WHERE sd.fieldid = 33
As I know we should use joins only for the columns which are preset in SELECT clause and for other joins we should implement using WHERE clause
Please try following query:
UPDATE en_inter.subscribers_data AS sd
inner join en_inter.list_subscribers AS ls
on sd.subscriberid = ls.subscriberid
LEFT JOIN (
SELECT pd1.email_address,COUNT(pd1.email_address) AS NumDowns
FROM email.papr_down AS pd1
INNER JOIN email.papr_data AS pd2 on pd1.paper_id = pd2.id
WHERE
email.papr_exam.id in (select exam from email.papr_data where exam = 1)
AND
email.papr_levl.id in (select level from email.papr_data where level = 4 )
AND
email.papr_subj.id in (select subject from email.papr_data)
GROUP BY email_address
) AS downs ON downs.email_address = ls.emailaddress
SET sd.data = ifnull(downs.NumDowns,1)
WHERE sd.fieldid = 33;
I can not execute this at my machine since i don't have the schema

I need get all records from table joined where at least one case with condition

I have three tables:
cp_projeto (id, nome...)
cp_habilidade_projeto (id, id_projeto)
cp_habilidade (id, nome...)
I need all projects with all cp_habilidade where cp_projeto have one cp_habilidade. My actual query:
SELECT
p.id as id_projeto,
p.nome as nome_projeto,
p.id_tipo_projeto,
p.dhPostagem,
cp_habilidade_projeto.id as id_habilidade_projeto,
cp_habilidade.nome as nome_habilidade
FROM (
SELECT * FROM cp_projeto
WHERE (id_status_projeto = 2)
ORDER BY dhPostagem DESC LIMIT 0, 10
) AS p
inner JOIN cp_habilidade_projeto ON (cp_habilidade_projeto.id_projeto = p.id)
inner JOIN cp_habilidade ON (cp_habilidade.id = cp_habilidade_projeto.id_habilidade)
JOIN cp_sub_categoria ON (cp_sub_categoria.id = p.id_sub_categoria)
WHERE (
p.nome like '%CSS%'
OR cp_habilidade.nome like '%CSS%'
)
This returns only cp_habilidade.nome = %CSS%, I need it all.
Thanks!
SELECT
p.id as id_projeto,
p.nome as nome_projeto,
p.id_tipo_projeto,
p.dhPostagem,
hp.id as id_habilidade_projeto,
h.nome as nome_habilidade
FROM cp_projecto p
JOIN cp_habilidade_projeto hp ON p.id = hp.id_projeto
JOIN cp_habilidade h ON h.id = hp.id_habilidade
WHERE p.id IN ( SELECT cp_habilidade_projeto.id_projeto
FROM cp_habilidade
JOIN cp_habilidade_projeto ON cp_habilidade.id = cp_habilidade_projeto.id_habilidade
WHERE cp_habilidade.nome LIKE '%CSS%' )