All I want to count entries based on date.(i.e entries with same date.)
My table is
You can see 5th and 6th entry have same date.
Now, the real problem as i think is the same date entry have different time so i am not getting what I want.
I am using this sql
SELECT COUNT( created_at ) AS entries, created_at
FROM wp_frm_items
WHERE user_id =1
GROUP BY created_at
LIMIT 0 , 30
What I am getting is this.
I want entries as 2 for date 2012-02-22
The reason you get what you get is because you also compare the time, down to a second apart. So any entries created the same second will be grouped together.
To achieve what you actually want, you need to apply a date function to the created_at column:
SELECT COUNT(1) AS entries, DATE(created_at) as date
FROM wp_frm_items
WHERE user_id =1
GROUP BY DATE(created_at)
LIMIT 0 , 30
This would remove the time part from the column field, and so group together any entries created on the same day. You could take this further by removing the day part to group entries created on the same month of the same year etc.
To restrict the query to entries created in the current month, you add a WHERE-clause to the query to only select entries that satisfy that condition. Here's an example:
SELECT COUNT(1) AS entries, DATE(created_at) as date
FROM wp_frm_items
WHERE user_id = 1
AND created_at >= DATE_FORMAT(CURDATE(),'%Y-%m-01')
GROUP BY DATE(created_at)
Note: The COUNT(1)-part of the query simply means Count each row, and you could just as well have written COUNT(*), COUNT(id) or any other field. Historically, the most efficient approach was to count the primary key, since that is always available in whatever index the query engine could utilize. COUNT(*) used to have to leave the index and retrieve the corresponding row in the table, which was sometimes inefficient. In more modern query planners this is probably no longer the case. COUNT(1) is another variant of this that didn't force the query planner to retrieve the rows from the table.
Edit: The query to group by month can be created in a number of different ways. Here is an example:
SELECT COUNT(1) AS entries, DATE_FORMAT(created_at,'%Y-%c') as month
FROM wp_frm_items
WHERE user_id =1
GROUP BY DATE_FORMAT(created_at,'%Y-%c')
You must eliminate the time with GROUP BY
SELECT COUNT(*) AS entries, created_at
FROM wp_frm_items
WHERE user_id =1
GROUP BY DATE(created_at)
LIMIT 0 , 30
Oops, misread it.
Use GROUP BY DATE(created_at)
Try:
SELECT COUNT( created_at ) AS entries, created_at
FROM wp_frm_items
WHERE user_id =1
GROUP BY DATE(created_at)
LIMIT 0 , 30
Related
Hello there I have the following doubt I want to count how many times in a month I enter data.
My database is:
Date:
10/2010
10/2010
09/2010
08/2010
I have the following query.
SELECT DISTINCT (date)
FROM employee
WHERE date
IN (SELECT date
FROM employee
GROUP BY date
HAVING count( date ) >0)
ORDER BY date DESC;
This query gives me:
Date:
10/2017
8/2017
9/2017
But I want you to give me something like that.
Count | Date
2 | 10/2017
1 | 9/2017
1 | 10/2017
I hope I have explained my regards.
You're overcomplicating it; no subquery, or DISTINCT, needed.
SELECT `date`, count(*)
FROM `employee`
GROUP BY `date`
HAVING count(*) > 0
ORDER BY `date` DESC;
I am a little confused as to what reason you would have for the HAVING count() > 0 though; the only way something could have a zero count would mean it wasn't in the table (and therefore wouldn't show up anyway).
Other observations:
DISTINCT is not a function; enclosing the date in parenthesis in the SELECT clause has absolutely no effect. (Also, DISTINCT is almost never appropriate for a GROUPing query.)
COUNT(somefield) is the same as COUNT(1), COUNT(*). If you want the count of unique values you can do COUNT(DISTINCT somefield); but it wouldn't make sense to COUNT(DISTINCT groupingfield) as that would always result in 1.
The query you wrote is a bit complicated. Distinct and group by are doing the same thing for you here. When you do a group by count will automatically give you the count of grouped rows. Also you will have unique dates as well. Try this.
SELECT count(date), date
FROM employee
GROUP BY date
HAVING count( date ) >0
ORDER BY date DESC;
I have a very simple table which consists of the following columns:
id | customer_id | total | created_at
I was running this query to get the results per day for the last ten days:
SELECT SUM(total) AS total, DATE_FORMAT(created_at, "%d/%m/%Y") AS date
FROM table
WHERE created_at BETWEEN "2017-02-20" AND "2017-03-01"
GROUP BY created_at
ORDER BY created_at DESC
This works fine, but I've just noticed that there's an issue with imported rows being duplicated for some reason so I'd like to update the query to be able to handle the situation if it ever happens again, in other words select one row instead of all when the date and customer id are the same (the total is also identical).
If I add customer_id to the group by that seems to work but the trouble with that is then the query returns a result per day for each customer when I only want the overall total.
I've tried a couple of things but I haven't cracked it yet, I think it will be achievable using a sub query and/or an inner join, I have tried this so far but the figures are very wrong:
SELECT
created_at,
(
SELECT SUM(total)
FROM table test
WHERE test.created_at = table.created_at
AND test.customer_id = table.customer_id
GROUP BY customer_id, created_at
LIMIT 1
) AS total
FROM table
WHERE created_at BETWEEN "2017-02-20" AND "2017-03-01"
GROUP BY created_at
ORDER BY created_at DESC
It's also a large table so finding a performant way to do this is also important.
First, are you sure that created_at is a date and not a datetime? This makes a big difference.
You can do what you want using two levels of aggregation:
SELECT SUM(max_total) AS total, DATE_FORMAT(created_at, '%d/%m/%Y') AS date
FROM (SELECT t.customer_id, t.created_at, MAX(total) as max_total
FROM table t
WHERE t.created_at BETWEEN '2017-02-20' AND '2017-03-01'
GROUP BY t.customer_id, t.created_at
) t
GROUP BY created_at
ORDER BY created_at DESC;
I've been tasked with converting a Rails app from MySQL to Postgres asap and ran into a small issue.
The active record query:
current_user.profile_visits.limit(6).order("created_at DESC").where("created_at > ? AND visitor_id <> ?", 2.months.ago, current_user.id).distinct
Produces the SQL:
SELECT visitor_id, MAX(created_at) as created_at, distinct on (visitor_id) *
FROM "profile_visits"
WHERE "profile_visits"."social_user_id" = 21
AND (created_at > '2015-02-01 17:17:01.826897' AND visitor_id <> 21)
ORDER BY created_at DESC, id DESC
LIMIT 6
I'm pretty confident when working with MySQL but I'm honestly new to Postgres. I think this query is failing for multiple reasons.
I believe the distinct on needs to be first.
I don't know how to order by the results of max function
Can I even use the max function like this?
The high level goal of this query is to return the 6 most recent profile views of a user. Any pointers on how to fix this ActiveRecord query (or it's resulting SQL) would be greatly appreciated.
The high level goal of this query is to return the 6 most recent
profile views of a user.
That would be simple. You don't need max() nor DISTINCT for this:
SELECT *
FROM profile_visits
WHERE social_user_id = 21
AND created_at > (now() - interval '2 months')
AND visitor_id <> 21 -- ??
ORDER BY created_at DESC NULLS LAST, id DESC NULLS LAST
LIMIT 6;
I suspect your question is incomplete. If you want:
the 6 latest visitors with their latest visit to the page
then you need a subquery. You cannot get this sort order in one query level, neither with DISTINCT ON, nor with window functions:
SELECT *
FROM (
SELECT DISTINCT ON (visitor_id) *
FROM profile_visits
WHERE social_user_id = 21
AND created_at > (now() - interval '2 months')
AND visitor_id <> 21 -- ??
ORDER BY visitor_id, created_at DESC NULLS LAST, id DESC NULLS LAST
) sub
ORDER BY created_at DESC NULLS LAST, id DESC NULLS LAST
LIMIT 6;
The subquery sub gets the latest visit per user (but not older than two months and not for a certain visitor21. ORDER BY must have the same leading columns as DISTINCT ON.
You need the outer query to get the 6 latest visitors then.
Consider the sequence of events:
Best way to get result count before LIMIT was applied
Why NULLS LAST? To be sure, you did not provide the table definition.
PostgreSQL sort by datetime asc, null first?
I'm in need of a better way of retrieving top 10 distinct UID from some tables I have.
The setup:
Table user_view_tracker
Contains pairs of {user id (uid), timestamp (ts)}
Is growing every day (today it's 41k entries)
My goal:
To produce a top 10 of most viewed user id's in the table user_view_tracker
My current code is working, but killing the database slowly:
select
distinct uvt.uid as UID,
(select count(*) from user_view_tracker temp where temp.uid=uvt.uid and temp.ts>date_sub(now(),interval 1 month)) as CLICK
from user_view_tracker uvt
order by CLICK
limit 10
It's quite obvious that a different data structure would help. But I can't do that as of now.
First of all, delete that subquery, this should be enough ;)
select
uvt.uid as UID
,count(*) as CLICK
from
user_view_tracker uvt
where
uvt.ts > date_sub(now(),interval 1 month)
group by
uvt.uid
order by CLICK DESC
limit 10
Try:
select uid, count(*) as num_stamps
from user_view_tracker
where ts > date_sub(now(), interval 1 month)
group by uid
order by 2 desc limit 10
I kept your criteria as far as getting the count for just the past month. You can remove that line if you want to count all.
The removal of DISTINCT should improve performance. It is not necessary if you aggregate in your outer query and group by uid, as that will aggregate the data to one row per uid with the count.
You should use Aggregate functions in MySQL
SELECT UID, COUNT(ts) as Number_Of_Views FROM user_view_tracker
GROUP BY UID
ORDER BY Number_Of_Views DESC
LIMIT 10
A simple demo which selects the top 10 UID viewed
http://sqlfiddle.com/#!2/907c10/3
I have a table that has a unique key each time a user creates a case:
id|doctor_id|created_dt
--|---------|-----------
1|23 |datetimestamp
2|23 |datetimestamp
3|17 |datetimestamp
How can I select and return the average amount of entries a user has per month?
I have tried this:
SELECT avg (id)
FROM `cases`
WHERE created_dt BETWEEN DATE_SUB(CURDATE(),INTERVAL 90 DAY) AND CURDATE()
and doctor_id = 17
But this returns a ridiculously large value that cannot be true.
To clarify: I am trying to get something like doctor id 17 has an average of 2 entries per month into this table.
I think you were thrown off by the idea of "averaging". You don't want the average id, or average user_id. You want the average number of entries into the table, so you would use COUNT():
SELECT count(id)/3 AS AverageMonthlyCases
FROM `cases`
WHERE created_dt BETWEEN DATE_SUB(CURDATE(),INTERVAL 90 DAY) AND CURDATE()
group by doctor_id
Since you have a 90 day interval, you want to count the number of rows per 30 days, or the count/3.
SELECT AVG(cnt), user_id
FROM (
SELECT COUNT(id) cnt, user_id
FROM cases
WHERE created_dt BETWEEN <yourDateInterval>
GROUP BY user_id, year(created_dt), month(created_dt)
)
Since you need average number of entries, AVG function is not really applicable, because it is SUM()/COUNT() and obviously you do not need that (why would you need SUM of ids).
You need something like this
SELECT
doctor_id,
DATE(created_dt,'%m-%Y') AS month,
COUNT(id) AS visits
FROM `cases`
GROUP BY
`doctor_id`,
DATE(created_dt,'%m-%Y')
ORDER BY
`doctor_id` ASC,
DATE(created_dt,'%m-%Y') ASC
To get visits per month per doctor. If you want to average it, you can then use something like
SELECT
doctor_id,
SUM(visits)/COUNT(month) AS `average`
FROM (
SELECT
doctor_id,
DATE(created_dt,'%m-%Y') AS month,
COUNT(id) AS visits
FROM `cases`
GROUP BY
`doctor_id`,
DATE(created_dt,'%m-%Y')
ORDER BY
`doctor_id` ASC,
DATE(created_dt,'%m-%Y') ASC
) t1
GROUP BY
doctor_id
Obviously you can add your WHERE clauses, as this query is compatible for multiple years (i.e. it will not count January of 2013th and January of 2014th as one month).
Also, it takes into account if a doctor has "blank" months, where he did not have any patients, so it will not count those months (0 can destroy and average).
Use this, you'll group each doctor's total id, by month.
Select monthname(created_dt), doctor_id, count(id) as total from cases group by 1,2 order by 1
Also you can use GROUP_CONCAT() as nested query in order to deploy a pivot like table, where each column is each doctor_id.