I have 2 tables one is users and second is locations
locations are one to many relationship with users.
I want to list all users based on latest location with condition distance(km) > 0.01. Please anyone?
I tried .syntax error (Query 1 ERROR: Unknown column 'd' in 'where clause')
SELECT *, (SELECT distance
from locations
where locations.user_id = users.id
order by created_at DESC
LIMIT 1
) as d
from users
where d > 0.01
Edit
tables
- users
- locations(multiple) (id,user_id,lat,lng,distance,created_at)
Expected result
- list of users(not duplicate) where latest locations contain distance less then 0.1 (double distance)
The derived column d is not allowed in the WHERE clause but you could use a HAVING clause:
having d > 0.01
Another way to get the results that you want, if you can't use window functions, is the join of your table to a query that uses NOT EXISTS to return the locations that you need:
select u.*, t.distance
from users u inner join (
select l.* from locations l
where not exists (select 1 from locations where user_id = l.user_id and created_at > l.created_at)
and l.distance > 0.01
) t on t.user_id = u.id
You can use window function :
select t.*
from (select u.*, l.*,
row_number() over (partition by u.id order by l.created_at desc) as seq
from users u inner join
locations l
on l.user_id = u.id
) t
where seq = 1 and distance > 0.01;
Related
I am trying to make a query to fetch the newest car for each user:
select * from users
left join
(select cars.* from cars
where cars.userid=users.userid
order by cars.year desc limit 1) as cars
on cars.userid=users.userid
It looks like it says Unknown column "users.userid" in where clause
I tried to remove cars.userid=users.userid part, but then it only fetches 1 newest car, and sticks it on to each user.
Is there any way to accomplish what I'm after? thanks!!
For this purpose, I usually use row_number():
select *
from users u left join
(select c.* , row_number() over (partition by c.userid order by c.year desc) as seqnum
from cars c
) c
on c.userid = u.userid and c.seqnum = 1;
One option is to filter the left join with a subquery:
select * -- better enumerate the columns here
from users u
left join cars c
on c.userid = u.userid
and c.year = (select max(c1.year) from cars c1 where c1.userid = c.userid)
For performance, consider an index on car(userid, year).
Note that this might return multiple cars per user if you have duplicate (userid, year) in cars. It would be better to have a real date rather than just the year.
Maybe there are better and more efficient way to query this. Here is my solution;
select users.userid, cars.*
from users
left join cars on cars.userid = users.userid
join (SELECT userid, MAX(year) AS maxDate
FROM cars
GROUP BY userid) as sub on cars.year = sub.maxDate;
I have 3 tables sc_user, sc_cube, sc_cube_sent
I wand to join to a user query ( sc_user) one distinct random message/cube ( from sc_cube ), that has not been sent to that user before ( sc_cube_sent), so each row in the result set has a disctinct user id and a random cubeid from sc_cube that is not part of sc_cube_sent with that user id associated there.
I am facing the problem that I seem not to be able to use a correlation id for the case that I need the u.id of the outer query in the inner On clause. I would need the commented section to make it work.
# get one random idcube per user not already sent to that user
SELECT u.id, sub.idcube
FROM sc_user as u
LEFT JOIN (
SELECT c.idcube, sent.idreceiver FROM sc_cube c
LEFT JOIN sc_cube_sent sent ON ( c.idcube = sent.idcube /* AND sent.idreceiver = u.id <-- "unknown column u.id in on clause" */ )
WHERE sent.idcube IS NULL
ORDER BY RAND()
LIMIT 1
) as sub
ON 1
I added a fiddle with some data : http://sqlfiddle.com/#!9/7b0bc/1
new cubeids ( sc_cube ) that should show for user 1 are the following : 2150, 2151, 2152, 2153
Edit>>
I could do it with another subquery instead of a join, but that has a huge performance impact and is not feasible ( 30 secs+ on couple of thousand rows on each table with reasonably implemented keys ), so I am still looking for a way to use the solution with JOIN.
SELECT
u.id,
(SELECT sc_cube.idcube
FROM sc_cube
WHERE NOT EXISTS(
SELECT sc_cube.idcube FROM sc_cube_sent WHERE sc_cube_sent.idcube = sc_cube.idcube AND sc_cube_sent.idreceiver = u.id
)
ORDER BY RAND() LIMIT 0,1
) as idcube
FROM sc_user u
without being able to test this, I would say you need to include your sc_user in the subquery because you have lost the scope
LEFT JOIN
( SELECT c.idcube, sent.idreceiver
FROM sc_user u
JOIN sc_cube c ON c.whatever_your_join_column_is = u.whatever_your_join_column_is
LEFT JOIN sc_cube_sent sent ON ( c.idcube = sent.idcube AND sent.idreceiver = u.id )
WHERE sent.idcube IS NULL
ORDER BY RAND()
LIMIT 1
) sub
If you want to get messagges ids that has not been sent to the particular user, then why use a join or left join at all ?
Just do:
SELECT sent.idcube
FROM sc_cube_sent sent
WHERE sent.idreceiver <> u.id
Then the query may look like this:
SELECT u.id,
/* sub.idcube */
( SELECT sent.idcube
FROM sc_cube_sent sent
WHERE sent.idreceiver <> u.id
ORDER BY RAND()
LIMIT 1
) as idcube
FROM sc_user as u
Got it working with NOT IN subselect in the on clause. Whereas the correlation link u.id is not given within the LEFT JOIN scope, it is for the scope of the ON clause. Here is how it works:
SELECT u.id, sub.idcube
FROM sc_user as u
LEFT JOIN (
SELECT idcube FROM sc_cube c ORDER BY RAND()
) sub ON (
sub.idcube NOT IN (
SELECT s.idcube FROM sc_cube_sent s WHERE s.idreceiver = u.id
)
)
GROUP BY u.id
Fiddle : http://sqlfiddle.com/#!9/7b0bc/48
Is there a possibility to do LEFT JOIN with only one row from other table ordered by column (date) without using sub query. My query is below. It works but it's super slow.
SELECT * FROM clients c
LEFT JOIN loan l ON c.id = l.id_client AND l.id = (
SELECT id FROM loan ll
WHERE ll.id_client = c.id
ORDER BY `create_date` DESC
LIMIT 1)
GROUP BY k.id DESC
ORDER BY c.register_date DESC
LIMIT n , m; (n,m is from pagination)
Is there a way to speed it up?
Im interpreting your question as "Get me all loan details for the most recent loan for each client"
This should work... note the assumption though.
SELECT *
FROM
clients c
LEFT JOIN (select id_client, Max(id) id -- this assumes that a loan with a later create date will also have a higher id.
from loan
group by id_client) il
on il.id_client = c.id
inner join loan l
on l.id = il.id
GROUP BY k.id DESC -- Dont know what "k" is
ORDER BY c.register_date DESC
LIMIT n , m; (n,m is from pagination)
I have a SQL query which does most of what I need it to do but I'm running into a problem.
There are 3 tables in total. entries, entry_meta and votes.
I need to get an entire row from entries when competition_id = 420 in the entry_meta table and the ID either doesn't exist in votes or it does exist but the user_id column value isn't 1.
Here's the query I'm using:
SELECT entries.* FROM entries
INNER JOIN entry_meta ON (entries.ID = entry_meta.entry_id)
WHERE 1=1
AND ( ( entry_meta.meta_key = 'competition_id' AND CAST(entry_meta.meta_value AS CHAR) = '420') )
GROUP BY entries.ID
ORDER BY entries.submission_date DESC
LIMIT 0, 25;
The votes table has 4 columns. vote_id, entry_id, user_id, value.
One option I was thinking of was to SELECT entry_id FROM votes WHERE user_id = 1 and include it in an AND clause in my query. Is this acceptable/efficient?
E.g.
AND entries.ID NOT IN (SELECT entry_id FROM votes WHERE user_id = 1)
A left join with an appropriate where clause might be useful:
SELECT
entries.*
FROM
entries
INNER JOIN entry_meta ON (entries.ID = entry_meta.entry_id)
LEFT JOIN votes ON entries.ID = votes.entry_id
WHERE 1=1
AND (
entry_meta.meta_key = 'competition_id'
AND CAST(entry_meta.meta_value AS CHAR) = '420')
AND votes.entry_id IS NULL -- This will remove any entry with votes
)
GROUP BY entries.ID
ORDER BY entries.submission_date DESC
Here's an implementation of Andrew's suggestion to use exists / not exists.
select
e.*
from
entries e
join entry_meta em on e.ID = em.entry_id
where
em.meta_key = 'competition_id'
and cast(em.meta_value as char) = '420'
and (
not exists (
select 1
from votes v
where
v.entry_id = e.ID
)
or exists (
select 1
from votes v
where
v.entry_id = e.ID
and v.user_id != 1
)
)
group by e.ID
order by e.submission_date desc
limit 0, 25;
Note: it's generally not a good idea to put a function inside a where clause (due to performance reasons), but since you're also joining on IDs you should be OK.
Also, The left join suggestion by Barranka may cause the query to return more rows than your are expecting (assuming that there is a 1:many relationship between entries and votes).
LEFT JOIN
(
SELECT user_id, review, COUNT(user_id) totalCount
FROM reviews
GROUP BY user_id
) b ON b.user_id= b.user_id
I am trying to fit WHERE LENGTH(review) > 100 in this somewhere but every I put it, it gives me problems.
The sub-query above counts all total reviews by user_id. I simply want to add one more qualification. Only count reviews greater than 100 length.
On a side note, I've seen the function CHAR_LENGTH -- not sure if that i what I need either.
EDIT:
Here is complete query working perfectly as expected for my needs:
static public $top_users = "
SELECT u.username, u.score,
(COALESCE(a.totalCount, 0) * 4) +
(COALESCE(b.totalCount, 0) * 5) +
(COALESCE(c.totalCount, 0) * 1) +
(COALESCE(d.totalCount, 0) * 2) +
(COALESCE(u.friend_points, 0)) AS totalScore
FROM users u
LEFT JOIN
(
SELECT user_id, COUNT(user_id) totalCount
FROM items
GROUP BY user_id
) a ON a.user_id= u.user_id
LEFT JOIN
(
SELECT user_id, COUNT(user_id) totalCount
FROM reviews
GROUP BY user_id
) b ON b.user_id= u.user_id
LEFT JOIN
(
SELECT user_id, COUNT(user_id) totalCount
FROM ratings
GROUP BY user_id
) c ON c.user_id = u.user_id
LEFT JOIN
(
SELECT user_id, COUNT(user_id) totalCount
FROM comments
GROUP BY user_id
) d ON d.user_id = u.user_id
ORDER BY totalScore DESC LIMIT 25;";
LENGTH() returns the length of the string measured in bytes. You probably want CHAR_LENGTH() as it will give you the actual characters.
SELECT user_id, review, COUNT(user_id) totalCount
FROM reviews
WHERE CHAR_LENGTH(review) > 100
GROUP BY user_id, review
You're also not using GROUP BY correctly.
See the documentation
The query that you want is:
LEFT JOIN
(
SELECT user_id, COUNT(user_id) totalCount,
sum(case when length(review) > 100 then 1 else 0 end
) as NumLongReviews
FROM reviews
GROUP BY user_id
) b ON b.user_id= b.user_id
This counts both the reviews and the "long" reviews. That count is done using a case statement nested in a sum() function.