I created this query and it only takes rows until date 23.11.2020 doesn't take more then 2-3 hundred rows.
SELECT a.datum
, a.cas
, a.domaci
, a.hoste
, a.stream
, b.name
, b.color2
, c.jmeno
, d.firstname as first1
, d.lastname as last1
, e.firstname as first2
, e.lastname as last2
FROM zapasy a
JOIN projekt b
ON b.id = a.projekt
JOIN televize c
ON c.id = a.televize
JOIN tipuser d
ON d.id = a.komentator1
JOIN tipuser e
ON e.id = a.komentator2
JOIN projekt_role f
ON f.userid = $uid
ORDER
BY datum DESC
, cas ASC
, domaci asc
, projekt asc
, stream ASC
Is there some kind of limit in SQL that just won't show me some rows if I use too many JOINS ?
Without knowing your data we can't diagnose this. But these aren't too many joins at all.
Suggestion: Remove your joins, one at a time, and look at the results. If, at any stage, you will get the rows that you are now missing, then you can try to find out why that particular join filtered them out.
Related
I try to improve this query but I do not made successefully. I use a some left join and subquerys (I don't know another form) We try to get all bookings from users with certain status and the number of bookings multiples related with this booking and get from the log user the origin. The query is slow even if use a limit clausure. I Appreciate all the help can you give me.
This is the query:
SELECT DISTINCT b.uneaque_id, b.id, b.status, b.route_status, b.username, b.purpose, b.transfer, b.pickup_date, b.pickup_time, b.return_time, b.amount, b.default_location, b.start_address_route_comments, b.start_address_route, b.end_address_route_comments, b.end_address_route, u1.first_name, u1.last_name, b.transaction_Id, b.manual_payment, mr.AddressCount, lu.origin
FROM bookingdetails b
LEFT JOIN log_users lu ON lu.uneaque_id = b.uneaque_id AND lu.command_type = 'NEW BOOKING'
LEFT JOIN (
SELECT booking_id, COUNT(*) AS AddressCount FROM booking_multiple_rides GROUP BY booking_id
) mr ON b.id = mr.booking_id,
userdetails u1 WHERE b.username = u1.email
AND u1.user_status IN ('Active', 'Blocked', 'Not_Active')
AND b.default_location = 1
PD: Sorry for my english.
You have a ON b.id = mr.booking_id, userdetails u1 WHERE
you should change with a proper inner join
SELECT DISTINCT b.uneaque_id
, b.id, b.status
, b.route_status
, b.username
, b.purpose
, b.transfer
, b.pickup_date
, b.pickup_time
, b.return_time
, b.amount
, b.default_location
, b.start_address_route_comments
, b.start_address_route
, b.end_address_route_comments
, b.end_address_route
, u1.first_name
, u1.last_name
, b.transaction_Id
, b.manual_payment
, mr.AddressCount
, lu.origin
FROM bookingdetails b
LEFT JOIN log_users lu ON lu.uneaque_id = b.uneaque_id AND lu.command_type = 'NEW BOOKING'
LEFT JOIN (
SELECT booking_id
, COUNT(*) AS AddressCount
FROM booking_multiple_rides GROUP BY booking_id
) mr ON b.id = mr.booking_id
INNER JOIN userdetails u1 ON b.username = u1.email
AND u1.user_status IN ('Active', 'Blocked', 'Not_Active')
AND b.default_location = 1
and be sure you have proper index on
table bookingdetails a composite index on columns ( uneaque_id , id, default_location)
table log_users a composite index on columns (uneaque_id, command_type)
table userdetails a cmposite index on columns (email,user_status )
Tip 1.
Hiding a derived table in a LEFT JOIN is a prescription for sluggishness.
Replace
mr.AddressCount
with
( SELECT COUNT(*)
FROM booking_multiple_rides
WHERE booking_id = b.id
GROUP BY booking_id ) AS AddressCount
and get rid of the LEFT JOIN ( SELECT ... ) AS mr ON ..
Tip 2 Use explicit JOINs, no the old-fashioned "comma-join":
JOiN userdetails u1
ON b.username = u1.email
This won't help performance but it will make things clearer.
Tip 3: If you need an INNER JOIN (u1) after a LEFT JOIN, use parentheses. Else, put the inner joins first, then the left joins. This makes it easier to use, but may screw up the logic.
Tip 4: Don't use LEFT unless you need it. When you dont need it, it confuses the reader (and the Optimizer). (Again, no performance change.)
Tip 5: Why are you using DISTINCT? That takes an extra pass over all the resultset.
If those do not help enough, then provide SHOW CREATE TABLE so we can critique the indexes.
I have query below:
SELECT t.t_id
, t.usr_idx
, t.t_is_for
, t.tg_ids
, t.created_time
, t.allow_reply
, u.usr_name
, u.usr_avatar
, u.show_profile
, IF(u.usr_timeline != '',CONCAT('https://s3.amazonaws.com/tuurnts3thumbnail/',u.usr_timeline),'') as usr_timeline
, u.node_userid
, t.t_time
FROM tuu_tuurnt t
JOIN tuu_user u
ON t.usr_idx = u.usr_idx
AND u.usr_state = 1
LEFT
JOIN tuu_post p
ON t.t_id = p.t_id
AND p.usr_idx = 44756
LEFT
JOIN tuu_friend f
ON f.frd_my_idx = 44756
AND f.frd_your_idx = t.usr_idx
LEFT
JOIN tuu_friend fl
ON fl.frd_your_idx = 44756
AND fl.frd_my_idx = t.usr_idx
WHERE t.status = 0
AND NOT EXISTS ( SELECT b.tuu_b_by_usr_idx
FROM tuu_blocked as b
WHERE b.tuu_b_usr_idx = 44756
AND t.usr_idx = b.tuu_b_by_usr_idx
)
GROUP
BY t.t_id
ORDER
BY t.t_time DESC
, t.t_id DESC
LIMIT 0,30;
It takes almost 7-8 second to give result but when I remove order by t.t_time and t.t_id then it runs within 1 sec max.
Is there anything I am doing wrong?
Without an index, MySQL must begin with the first row and then read through the entire table to find the relevant rows. The larger the table, the more this costs. See How MySQL Uses Indexes for details. See also this topic about using indexes and aliases together.
cI'm seeking some help with my left join with a limit.
What i'm trying to do is to loop through my users and check in another table if there's problems connected to the user.
But currently I'm getting all kinds of weird results and it does not LIMIT the result for each user and it also lists column status_link_missing = 0 even though i have told the sub query to only list status_link_missing = 1
So I'm stuck for now, help is much appreciated!
SELECT
a.user_id AS settings_userid
, a.contact_interval
, b.user_id
, b.notify_user
, b.status_host_down
, b.status_link_missing
, b.status_relnofollow
FROM `link_exchange_settings` a
LEFT JOIN link_exchange_links b
ON b.id
= ( SELECT c.id
FROM link_exchange_links AS c
WHERE
b.user_id = a.user_id
AND c.notify_user = 1
AND c.status_link_missing = 1
LIMIT 1
)
WHERE a.allow_contact = 1
LIMIT 10
Edit
I switched SELECT b.id to c.id now and LIMIT works but now it only works for the first user
Try this change (no reference to b in the subquery):
SELECT
a.user_id AS settings_userid
, a.contact_interval
, b.user_id
, b.notify_user
, b.status_host_down
, b.status_link_missing
, b.status_relnofollow
FROM `link_exchange_settings` a
LEFT JOIN link_exchange_links b
ON b.id
= ( SELECT c.id -- changed
FROM link_exchange_links AS c
WHERE
c.user_id = a.user_id -- changed
AND c.notify_user = 1
AND c.status_link_missing = 1
-- ORDER BY c.something -- optional, recommended addition
LIMIT 1
)
WHERE a.allow_contact = 1
-- ORDER BY a.something_else -- optional, recommended addition
LIMIT 10 ;
It's also good to have ORDER BY when you use LIMIT. Unless you want indeterminate results.
You are using "c.status_link_missing = 1" in sub-query but if you will use it in WHERE clause with "AND" you will get your desired results.
In fact you have to decide and use appropriate condition in WHERE clause of main query instead of LEFT JOIN sub-query.
I have this query:
SELECT Concat(f.name, ' ', f.parent_names) AS FullName,
stts.name AS 'Status',
u.name AS Unit,
city.name AS City,
(SELECT Group_concat(c.mobile1)
FROM contacts c
WHERE c.id = f.husband_id
OR c.id = f.wife_id) AS MobilePhones,
f.phone AS HomePhone,
f.contact_initiation_date AS InitDate,
f.status_change_date AS StatusChangeDate,
cmt.created_at AS CommentDate,
cmt.comment AS LastComment,
f.reconnection_date AS ReconnectionDate,
(SELECT Group_concat(t.name, ' ')
FROM taggings tgs
JOIN tags t
ON tgs.tag_id = t.id
WHERE tgs.taggable_type = 'family'
AND tgs.taggable_id = f.id) AS HandlingStatus
FROM families f
JOIN categories stts
ON f.family_status_cat_id = stts.id
JOIN units u
ON f.unit_id = u.id
JOIN categories city
ON f.main_city_cat_id = city.id
LEFT JOIN comments cmt
ON f.last_comment_id = cmt.id
WHERE 1 = 0
OR ( u.is_busy = 1 )
OR ( f.family_status_cat_id = 1423 )
OR ( f.family_status_cat_id = 1422
AND f.status_change_date BETWEEN '2011-03-21' AND '2012-03-13' )
My problem is very specific. It is regarding the line:
SELECT GROUP_CONCAT( c.mobile1 )
FROM contacts c
WHERE c.id = f.husband_id
OR c.id = f.wife_id
) AS MobilePhones
When I use EXPLAIN, it seems that this query is bad. I get for this table (c = contacts): 38307 rows.
On what columns should I put the index according to the query?
I tried mobile1 - but no improvement (BTW - family_id is indexed in the contacts table).
I attach the image of the explain result:
Or maybe someone can help me optimize the query...
Any column you'll be searching on, to speed up the process. Keep in mind that keys are already indexed.
Well, it seems that using the GROUP_CONCAT is the problem.
I just seperated the wife and husband mobile to be 2 different columns.
First, I thought that using the GROUP_CONCAT will be faster, but it proved to be VERY WRONG.
Just out of my curiosity, what is the performance of the query
SELECT GROUP_CONCAT( c.mobile1 )
FROM contacts c
WHERE c.id IN(f.husband_id, f.wife_id)
) AS MobilePhones
I have this query, but it takes about 15 seconds to finish.. how can i simplyfy it to get same result in less time? my problem is that i need all of this data at ones.
SELECT * FROM (
SELECT c.client_id, c.client_name, c.client_bpm,
c.client_su_name, c.client_maxbpm, s.bpm,
s.timestamp, m.mesure_id, ms.currentT
FROM tbl_clients c, tbl_meting m, tbl_sensor_meting s,
tbl_magsens_meting ms
WHERE c.client_id = m.client_id
AND (m.mesure_id = s.id_mesure
OR m.mesure_id = ms.id_mesure)
AND m.live =1
ORDER BY s.timestamp DESC
) AS mesure
GROUP BY mesure.client_id
I think the problem may be the OR condition from your WHERE clause? You seem to be trying to join to one table or another, which you can't do. So I've replaced it with a LEFT JOIN, so in the event no related records exist nothing will be returned.
I also took out your GROUP BY, as I don't think it was required.
SELECT c.client_id, c.client_name, c.client_bpm,
c.client_su_name, c.client_maxbpm, s.bpm,
s.timestamp, m.mesure_id, ms.currentT
FROM tbl_clients c
JOIN tbl_meting m ON m.client_id = c.client_id
LEFT JOIN tbl_sensor_meting s ON s.id_mesure = m.mesure_id
LEFT JOIN tbl_magsens_meting ms ON ms.id_mesure = m.mesure_id
WHERE m.live = 1
ORDER BY s.timestamp DESC