I would like to return a product together with its latest value and values from last hour.
I have a product-table :
id, name, type (and so on)...
I have a values-table :
id_prod, timestamp, value
Something like :
12:00:00 = 10
12:15:00 = 10
12:30:00 = 10
12:45:00 = 10
13:00:00 = 10
13:15:00 = 10
13:30:00 = 10
I would like a query that returns the latest value (13:30:00) together with the sum of values one hour back. This should return:
time = 13:30:00
latestread = 10
lasthour = 40
What I almost got working was:
SELECT *,
(SELECT value FROM values S WHERE id_prod=P.id
ORDER BY timestamp DESC LIMIT 1) as latestread,
(SELECT sum(value) FROM values WHERE id_prod=D.id and
date_created>SUBTIME(S.date_created,'01:00:00')) as trendread
FROM prod P ORDER BY name
But this fails with "Unknown column 'S.date_created' in 'where clause'"
Any suggestions?
If I understand correctly what you're trying to do, then You would have something like:
SELECT p.id, max(date_created), sum(value), mv.max_value
FROM product p
JOIN values v on p.id = v.product_id
JOIN (SELECT product_id, value as max_value
FROM values v2
WHERE date_created = (SELECT max(date_created) FROM values WHERE product_id=v2.product_id)) mv on product_id=p.id
WHERE date_created between DATE_SUB(now(), INTERVAL 1 HOUR)) and now()
GROUP BY p.id
ORDER BY p.id
Aleks G and mhasan gave solutions, but not the reason why this fails. The reason this fails is because the alias S is not known inside the subquery. Subqueries have no knowledge about the tables outside their scope.
You have missed providing alias for table Values in subquery below
SELECT *,
(SELECT value FROM values S WHERE id_prod=P.id
ORDER BY timestamp DESC LIMIT 1) as latestread,
(SELECT sum(value) FROM values S WHERE id_prod=P.id and
date_created>SUBTIME(S.date_created,'01:00:00')) as trendread
FROM prod P ORDER BY name
I think this is the query that you are trying to write:
SELECT p.*,
(SELECT v.value
FROM values v
WHERE v.id_prod = p.id
ORDER BY v.timestamp DESC
LIMIT 1
) as latestread,
(SELECT sum(v.value)
FROM values v
WHERE v.id_prod = p.id and
v.timestamp > SUBTIME(now(), '01:00:00')
) as trendread
FROM prod p
ORDER BY p.name;
This changes all the aliases to be abbreviations for the table name. It also fixes the expression for the last hour by using now() and gets rid of date_created which doesn't seem to be in either table based on the question. The query conveniently assumes that timestamp is a datetime. If it is a unix timestamp, then somewhat different time logic is necessary.
This should be reasonably efficient with an index on values(id_prod, timestamp, value).
Related
price | date | product_id
100 | 2020-09-21 | 1
400 | 2020-09-20 | 2
300 | 2020-09-20 | 3
200 | 2020-09-19 | 1
400 | 2020-09-18 | 2
I add an entry into this table every day with a product's price that day.
Now I want to get most price drops for the last week (all dates up to 2020-09-14), in this example it would only return the product_id = 1, because that's the only thing that changed.
I think I have to join the table to itself, but I'm not getting it to work.
Here's something that I wanted to return the most price changes over the last day, however it's not working.
select pt.price, pt.date, pt.product_id, (pt.price - py.price) as change
from prices as pt
inner join (
select *
from prices
where date > '2020-09-20 19:33:43'
) as py
on pt.product_id = py.product_id
where pt.price - py.price > 0
order by change
I understand that you want to count how many times the price of each product changed over the last 7 days.
A naive approach would use aggregation and count(distinct price) - but it fails when a product's price changes back and forth.
A safer approach is window functions: you can use lag() to retrieve the previous price, and compare it against the current price; it is then easy to aggregate and count the price changes:
select product_id, sum(price <> lag_price) cnt_price_changes
from (
select t.*, lag(price) over(partition by product_id order by date) lag_price
from mytable t
where date >= current_date - interval 7 day
) t
group by product_id
order by price_changes desc
Try using MAX() and MIN() instead....
select MAX(pt.price), MIN(pt.price), MAX(pt.price) - MIN(pt.price) as change
from prices as pt
inner join (
select *
from prices
where date > '2020-09-20 19:33:43'
) as py
on pt.product_id = py.product_id
order by change
Instead of subtracting every row by every other row to get the result, you can find the max and min's easily by means of MAX() and MIN(), and, ultimately, **MAX() - MIN()**. Relevant lines from the linked MySQL documentation...
MAX(): Returns the maximum value of expr.
MIN(): Returns the minimum value of expr.
You won't be able to pull the other fields (id's, dates) since this is a GROUP BY() implied by the MAX() and MIN(), but you should then be able to get that info by query SELECT * FROM ... WHERE price = MAX_VALUE_JUST_ACQUIRED.
This examples will get you results per WeekOfYear and WeekOfMonth regarding the lowering of the price per product.
SELECT
COUNT(m1.product_id) as total,
m1.product_id,
WEEK(m1.ddate) AS weekofyear
FROM mytest m1
WHERE m1.price < (SELECT m2.price FROM mytest m2 WHERE m2.ddate<m1.ddate AND m1.product_id=m2.product_id LIMIT 0,1)
GROUP BY weekofyear,m1.product_id
ORDER BY weekofyear;
SELECT
COUNT(m1.product_id) as total,
m1.product_id,
FLOOR((DAYOFMONTH(ddate) - 1) / 7) + 1 AS weekofmonth
FROM mytest m1
WHERE m1.price < (SELECT m2.price FROM mytest m2 WHERE m2.ddate<m1.ddate AND m1.product_id=m2.product_id LIMIT 0,1)
GROUP BY weekofmonth,m1.product_id
ORDER BY weekofmonth;
Try this out in SQLFiddle.
If I have the following table in MySQL:
date type amount
2017-12-01 3 2
2018-01-01 1 100
2018-02-01 1 50
2018-03-01 2 2000
2018-04-01 2 4000
2018-05-01 3 2
2018-06-01 3 1
...is there a way to find the sum of the amounts corresponding to the latest dates of each type? There are guaranteed to be no duplicate dates for any given type.
The answer I'd be looking to get from the data above could broken down like this:
The latest date for type 1 is 2018-02-01, where the amount is 50;
The latest date for type 2 is 2018-04-01, where the amount is 4000;
The latest date for type 3 is 2018-06-01, where the amount is 1;
50 + 4000 + 1 = 4051
Is there a way to arrive directly at 4051 in a single query? This is for a Django project using MySQL if that makes a difference; I wasn't able to find an ORM-related solution either, so figured a raw SQL query might be a better place to start.
Thanks!
Not sure for Django but in raw sql you could use a self join to pick latest row for each type based on latest date and then aggregate your results to get the sum of amounts for each type
select sum(a.amount)
from your_table a
left join your_table b on a.type = b.type
and a.date < b.date
where b.type is null
Demo
Or
select sum(a.amount)
from your_table a
join (
select type, max(date) max_date
from your_table
group by type
) b on a.type = b.type
and a.date = b.max_date
Demo
Or by using a correlated subuery
select sum(a.amount)
from your_table a
where a.date = (
select max(date)
from your_table
where type = a.type
)
Demo
For Mysql 8 you can use window functions to get you desired result as
select sum(amount)
from (select *, row_number() over (partition by type order by date desc) as seq
from your_table
) t
where seq = 1;
Demo
I have the following query:
set #cumulativeSum := 0;
select
(#cumulativeSum:= #cumulativeSum + (count(distinct `ce`.URL, `ce`.`IP`))) as `uniqueClicks`,
cast(`ce`.`dt` as date) as `createdAt`
from (SELECT DISTINCT min((date(CODE_EVENTS.CREATED_AT))) dt, CODE_EVENTS.IP, CODE_EVENTS.URL
FROM CODE_EVENTS
GROUP BY CODE_EVENTS.IP, CODE_EVENTS.URL) as ce
join ATTACHMENT on `ce`.URL = ATTACHMENT.`ID`
where ATTACHMENT.`USER_ID` = 6
group by cast(`ce`.`dt` as date)
ORDER BY ce.URL;
It works almost ok, I would like to have as result set a date and amount of cumulative sum as uniqueClicks, the problem is that in my result set it is not added up together.
uniqueClicks createdAt
1 2018-02-01
3 2018-02-03
1 2018-02-04
and I'd like to have
uniqueClicks createdAt
1 2018-02-01
4 2018-02-03
5 2018-02-04
I believe you can obtain a rolling sum of the unique clicks without needing to resort to dynamic SQL:
SELECT
t1.CREATED_AT,
(SELECT SUM(t2.uniqueClicks) FROM
(
SELECT CREATED_AT, COUNT(DISTINCT IP, URL) uniqueClicks
FROM CODE_EVENTS
GROUP BY CREATED_AT
) t2
WHERE t2.CREATED_AT <= t1.CREATED_AT) uniqueClicksRolling
FROM
(
SELECT DISTINCT CREATED_AT
FROM CODE_EVENTS
) t1
ORDER BY t1.CREATED_AT;
The subquery aliased as t2 computes the number of unique clicks on each given day which appears in your table. The distinct count of IP and URL is what determines the number of clicks. We can then subquery this intermediate table and sum clicks for all days up and including the current date. This is essentially cursor style action, and can replace your use of session variables.
In a MYSQL table with those 5 fields: id, user_id, date, type, uid where type can be 1 or 2, I'm looking for a single query where I can fetch 2 results, one for type=1 and another one for type=2 based on date field.
Right now i have the following query which only gives me the last uid without taking care of the type field.
SELECT t.uid
FROM table AS t
WHERE t.user_id = 666
ORDER BY t.date
DESC LIMIT 1
Does anyone know how should modify this query so i can get the last uid for type=1 and the last one for type=2 based on date field? I would like to keep a a single query
Union all is probably the simplest method:
(select t.*
from t
where t.user_id = 666 and t.type = 1
order by date desc
limit 1
) union all
(select t.*
from t
where t.user_id = 666 and t.type = 2
order by date desc
limit 1
)
Finally i updated the query following this "paradigm":
http://dev.mysql.com/doc/refman/5.7/en/example-maximum-column-group-row.html
http://jan.kneschke.de/projects/mysql/groupwise-max/
This is how the query ended up:
SELECT s1.type, s1.uid
FROM t AS s1
LEFT JOIN t AS s2 ON s1.type = s2.type AND s1.date < s2.date
WHERE s2.date IS NULL;
Here's a visual example: http://hastebin.com/ibinidasuw.vhdl
Credits are for snoyes from #sql on Freenode. :)
I am storing the response to various rpc calls in a mysql table with the following fields:
Table: rpc_responses
timestamp (date)
method (varchar)
id (varchar)
response (mediumtext)
PRIMARY KEY(timestamp,method,id)
What is the best method of selecting the most recent responses for all existing combinations of method and id?
For each date there can only be one response for a given method/id.
Not all call combinations are necessarily present for a given date.
There are dozens of methods, thousands of ids and at least 365 different dates
Sample data:
timestamp method id response
2009-01-10 getThud 16 "....."
2009-01-10 getFoo 12 "....."
2009-01-10 getBar 12 "....."
2009-01-11 getFoo 12 "....."
2009-01-11 getBar 16 "....."
Desired result:
2009-01-10 getThud 16 "....."
2009-01-10 getBar 12 "....."
2009-01-11 getFoo 12 "....."
2009-01-11 getBar 16 "....."
(I don't think this is the same question - it won't give me the most recent response)
This solution was updated recently.
Comments below may be outdated
This can query may perform well, because there are no joins.
SELECT * FROM (
SELECT *,if(#last_method=method,0,1) as new_method_group,#last_method:=method
FROM rpc_responses
ORDER BY method,timestamp DESC
) as t1
WHERE new_method_group=1;
Given that you want one resulting row per method this solution should work, using mysql variables to avoid a JOIN.
FYI, PostgreSQL has a way of doing this built into the language:
SELECT DISTINCT ON (method) timestamp, method, id, response
FROM rpc_responses
WHERE 1 # some where clause here
ORDER BY method, timestamp DESC
Self answered, but I'm not sure that it will be an efficient enough solution as the table grows:
SELECT timestamp,method,id,response FROM rpc_responses
INNER JOIN
(SELECT max(timestamp) as timestamp,method,id FROM rpc_responses GROUP BY method,id) latest
USING (timestamp,method,id);
Try this...
SELECT o1.id, o1.timestamp, o1.method, o1.response
FROM rpc_responses o1
WHERE o1.timestamp = ( SELECT max(o2.timestamp)
FROM rpc_responses o2
WHERE o1.id = o2.id )
ORDER BY o1.timestamp, o1.method, o1.response
...it even works in Access!
i used this,worked for me
select max(timestamp),method,id from tables where 1 group by method,id order by timestamp desc
Subquery is very taxing when the data set becomes larger.
Try this:
SELECT t1.*
FROM rpc_responses AS t1
INNER JOIN rpc_responses AS t2
GROUP BY t1.method, t1.id, t1.timestamp
HAVING t1.timestamp=MAX(t2.timestamp)
ORDER BY t1.timestamp, t1.method, t1.response;
Checking the three main answers in some other use case shows that the most voted answer is also by far the fastest, swarm intelligence works here:
# Answer 1: https://stackoverflow.com/a/12625667/11154841
# 165ms
SELECT
COUNT(0)
FROM
(
SELECT
mtn.my_primary_key,
mtn.my_info_col,
IF(#last_my_primary_key = my_primary_key,
0,
1) AS new_my_primary_key_group,
#last_my_primary_key := my_primary_key
FROM
my_db_schema.my_table_name mtn
WHERE
mtn.date_time_col > now() - INTERVAL 1 MONTH
ORDER BY
my_primary_key,
mtn.date_time_col DESC
) AS t1
WHERE
new_my_primary_key_group = 1
AND t1.my_info_col = 'delete';
# Answer 2: https://stackoverflow.com/a/435709/11154841
# 757ms
SELECT
count(0)
FROM
my_db_schema.my_table_name mtn
JOIN
(
SELECT
my_primary_key,
max(date_time_col) AS date_time_col
FROM
my_db_schema.my_table_name mtn
WHERE
mtn.date_time_col > now() - INTERVAL 1 MONTH
GROUP BY
mtn.my_primary_key) latest
USING (my_primary_key,
date_time_col)
WHERE
mtn.my_info_col = 'delete';
# Answer 3: https://stackoverflow.com/a/3185644/11154841
# 1.310s
SELECT
count(0)
FROM
my_db_schema.my_table_name mtn
WHERE
mtn.date_time_col = (
SELECT
max(mtn2.date_time_col)
FROM
my_db_schema.my_table_name mtn2
WHERE
mtn2.my_primary_key = mtn.my_primary_key
AND mtn2.date_time_col > now() - INTERVAL 1 MONTH
)
AND mtn.date_time_col > now() - INTERVAL 1 MONTH
AND mtn.my_info_col = 'delete';
The concept of "most recent" is fairly vague. If you mean something like the 100 most recent rows then you can just add a TOP(100) to your SELECT clause.
If you mean the "most recent" based on a the most recent date then you can just do
SELECT timestamp,method,id,response
FROM rpc_responses
HAVING max(timestamp) = timestamp
...is more than one year later but i might help someone
To select all the queries starting from latest
SELECT *
FROM rpc_responses
ORDER BY timestamp DESC