Limit MySQL results by left join - mysql

I have a MySQL query that creates an aggregate of data for an object and all of it's children in a one to many relationship. My query looks like this:
select * from object o
left join event e on o.tenant_id = e.tenant_id AND o.udid = e.udid
left join event_type et on e.event_type_id = et.event_type_id
left join event_custom_field ecf on e.event_id = ecf.event_id
left join profile p on o.tenant_id = p.tenant_id AND o.udid = p.udid
left join status s on o.tenant_id = s.tenant_id AND o.udid = s.udid
left join o_tenant_app ota on o.tenant_id = ota.tenant_id AND o.udid = ota.udid
left join tenant_app ta on ota.tenant_app_id = ta.tenant_app_id
left join heartbeat h on o.tenant_id = h.tenant_id AND o.udid = h.udid
where o.tenant_id = 'a'
AND o.checked_out = false
and p.name in ('test')
and s.status_name in ('stat1', 'stat2')
order by o.udid, e.event_id;
I need to be able to apply a limit to the number of objects returned while still including all of the other joined data. If I put the limit at the end then I will lose object data. I could do this on my first line:
select * from (select * from object limit 0,5) o
but that will show fewer than 5 objects if those first 5 objects don't match the where clause. I would like to do this as performant as possible as I will likely have millions of records to query against.

Related

MYSQL Inner Join with IF Statement

I'm trying to join several tables in my database.
I need to get account information from the 'accounts' table with the latest meter history on it.
And if an account has no meter history, I want it to show 'meter' related fields as NULL.
Here's my query so far:
SELECT
accounts.id,
accounts.account_order,
acc.id AS accounts_class_id,
acc.zone,
acc.book,
acc.service_class,
acc.size,
acc.account_no AS series_no,
accounts.status,
application_address.address_line,
concessionaires.firstname,
concessionaires.middlename,
concessionaires.lastname,
mb.brand_name,
m.meter_no,
ms.meter_status
FROM
accounts
INNER JOIN
applications
ON accounts.application_id = applications.id
LEFT JOIN
application_address
ON applications.application_no = application_address.application_no
LEFT JOIN
concessionaires
ON applications.concessionaire_no = concessionaires.concessionaire_no
INNER JOIN
accounts_classifications acc
ON accounts.id = acc.account
INNER JOIN meter_history mh
ON mh.id = (SELECT id FROM meter_history mh2
WHERE mh2.account_id = accounts.id
ORDER BY mh2.status_date DESC
LIMIT 1)
LEFT JOIN
meter_status ms
ON mh.meter_status = ms.id
INNER JOIN
meter m
ON mh.meter = m.id
LEFT JOIN
meter_brand mb
ON m.meter_brand = mb.id
WHERE
acc.book = 1 AND acc.zone = 20 AND applications.status = '6' AND acc.status = '1'
This would return only accounts with meter history on it.
Where should I put my IF condition so I get accounts with no history as well, or if that is even possible with my query. Thank you!

MySQL: From sub query to a single query

I have this query which i believe can be optimized:
SELECT floors.id, floors.floor FROM floors
WHERE floors.societies_id = 1
AND floors.status = 'Y'
AND floors.id NOT IN (
SELECT DISTINCT(floors.id) FROM floors
INNER JOIN societies ON societies.id = floors.societies_id
INNER JOIN resident_floors ON resident_floors.floors_id = floors.id
WHERE societies.id = 1
AND floors.status = 'Y'
)
Is this query fine to use or there it can be improved..?
It looks like you want to get all floors that aren't present in resident_floors. For this we can left join RF in and ask for only rows where the join failed resulting in a null in RF:
SELECT floors.* FROM floors
INNER JOIN societies ON societies.id = floors.societies_id
LEFT JOIN resident_floors ON resident_floors.floors_id = floors.id
WHERE societies.id = 1
AND floors.status = 'Y'
AND resident_floors.floors_id IS NULL

SQL - return rows that do not have a certain value

looking for a bit of help here if possible?
I have the following query:-
On or database we have a table called Linkfile, in this table are "Types" all beginning with "YG". I need to return those rows that do not have the type of "YG8" but just cannot seem to do it. I know ill need to use a sub query but am stuck!
This is my code and the fields I need to return. I just need to only show those that do not have the lk.type of "YG8"
select distinct l.description, p.displayname AS Temp, p.compliance_status As 'Compliant', lk.displayname, lk.type
from event e
inner join organisation o on e.organisation_ref = o.organisation_ref
inner join opportunity opp on e.opportunity_ref = opp.opportunity_ref
inner join event_role ev on ev.event_ref = e.event_ref
inner join address a on a.address_ref = opp.address_ref
inner join person p on ev.person_ref = p.person_ref
inner join lookup l on p.responsible_team = l.code
inner join person_type pt on p.person_ref = pt.person_ref
inner join linkfile lk on lk.parent_object_ref = pt.person_ref
where o.displayname LIKE '%G4S%' and p.compliance_category = '$016'
and lk.type like 'YG%' and l.code_type = '2'
and a.displayname LIKE '%MOJ%'
and pt.status = 'A'
order by l.description, p.displayname, lk.type
Use below query :
select distinct l.description, p.displayname AS Temp, p.compliance_status As 'Compliant', lk.displayname, lk.type,lk.parent_object_ref
from event e
inner join organisation o on e.organisation_ref = o.organisation_ref
inner join opportunity opp on e.opportunity_ref = opp.opportunity_ref
inner join event_role ev on ev.event_ref = e.event_ref
inner join address a on a.address_ref = opp.address_ref
inner join person p on ev.person_ref = p.person_ref
inner join lookup l on p.responsible_team = l.code
inner join person_type pt on p.person_ref = pt.person_ref
left join (select displayname, type,parent_object_ref from linkfile where lk.type like 'YG8%' )lk on lk.parent_object_ref = pt.person_ref
where o.displayname LIKE '%G4S%' and p.compliance_category = '$016' and lk.parent_object_ref is null
and l.code_type = '2'
and a.displayname LIKE '%MOJ%'
and pt.status = 'A'
order by l.description, p.displayname, lk.type;
I've used left join on linkfile with type like 'YG8%' and fetching the only records which are not matched
I think you can just replace the
lk.type like 'YG%'
with the following:
(lk.type >= 'YG' and lk.type <'YG8') or (lk.type > 'YG8' and lk.type <='YGZ')
this should accomplish what you are trying to do and also avoid using "like" which is less efficient (assuming you have an index on lk.type, at least).
You may refine this a bit by knowing which are the possible values of lk.type of course. I.e. what are the extremes for the YG "subtype"? YG00-YG99? YG-YGZ?
(Be especially careful if you may have YG81 or YG87 for example, because then my clause will not work properly... on the other hand if your YG subtype can have values like YG34 it would have been better to use YG08 instead of YG8)

error subquery return more than 1 when doing multiple select

I want to do a multiple select in one query with different conditions. but somehow i'm stuck in this problem. any idea?
SELECT
(select io_link_event_names.name from doors left join controller_devices on doors.iid = controller_devices.iid left join events on controller_devices.mac = events.mac left join io_link_event_names on events.iolinkerid = io_link_event_names.extra where events.iolinkerid = "9000;1") AS forced,
(select doors.name FROM doors) AS doorname
ERROR #1242 - Subquery returns more than 1 row
consider this
SELECT d.[forced], doors.name as doorname
from doors
left join (
select controller_devices.iid, io_link_event_names.name as [forced]
from events
inner join controller_devices on controller_devices.mac = events.mac
inner join io_link_event_names on events.iolinkerid = io_link_event_names.extra
where events.iolinkerid = "9000;1"
) as d on d.iid = doors.iid
If you have more than 1 row in table doors, you get this error. If you want too see door name relevant to event selected in first query, use
select io_link_event_names.name,
doors.name doorname
from doors
left join controller_devices
on doors.iid = controller_devices.iid
left join events
on controller_devices.mac = events.mac
left join io_link_event_names
on events.iolinkerid = io_link_event_names.extra
where events.iolinkerid = "9000;1"

mysql inner join return null value,

SELECT `mpeda_fish`.`id`, `mpeda_fish`.`fish` as analysis, sum(mpeda_fishdetails.quantity) as qty
FROM (`mpeda_fishdetails`)
INNER JOIN `mpeda_scientificfish` ON `mpeda_scientificfish`.`id` = `mpeda_fishdetails`.`scientificfish`
INNER JOIN `mpeda_fish` ON `mpeda_fish`.`id` = `mpeda_scientificfish`.`fish`
INNER JOIN `mpeda_fishcatch` ON `mpeda_fishcatch`.`id` = `mpeda_fishdetails`.`fishcatch`
INNER JOIN `mpeda_harbour` ON `mpeda_harbour`.`id` = `mpeda_fishcatch`.`harbour`
WHERE `mpeda_fishcatch`.`status` = 1
ORDER BY `mpeda_fishdetails`.`id` ASC
this query gets 2 columns null value and one column gets data inside why?
You use the SUM() function. In order to get meaningful results you should have a group by clause.
SELECT `mpeda_fish`.`id`, `mpeda_fish`.`fish` as analysis, sum(mpeda_fishdetails.quantity) as qty
FROM (`mpeda_fishdetails`)
INNER JOIN `mpeda_scientificfish` ON `mpeda_scientificfish`.`id` = `mpeda_fishdetails`.`scientificfish`
INNER JOIN `mpeda_fish` ON `mpeda_fish`.`id` = `mpeda_scientificfish`.`fish`
INNER JOIN `mpeda_fishcatch` ON `mpeda_fishcatch`.`id` = `mpeda_fishdetails`.`fishcatch`
INNER JOIN `mpeda_harbour` ON `mpeda_harbour`.`id` = `mpeda_fishcatch`.`harbour`
WHERE `mpeda_fishcatch`.`status` = 1
GROUP BY `mpeda_fish`.`id`, `mpeda_fish`.`fish`
ORDER BY `mpeda_fishdetails`.`id` ASC