I have a table with 2 columns
organization_id | user_name
1 | abc
1 | xyz
2 | bhi
2 | ipq
2 | sko
3 | ask
...
Each organization could have any number of users ranging from 1 to 100, 2000 and so on.
I wanted to show them in grafana in a table as following:
organization_id | user_name
1 | abc, xyz
2 | bhi, ipq, sko
3 | ask
Since there could be many users I want to show any 10 users belonging to same organization.
The database here is timescale db, the table is also a time series table showing when user was registered
If I understand rightly that you want 10 users per organisation you can use the query below.
I have added group by in the CTE to avoid returning duplicate user_name's.
In the test schema there are duplicate values of 'pqr' for organisation 2 but this username is only returned once even though there are less then 10 user_name's for 2
test schema db Fiddle here
With topTen as
(Select
Organisation_id,
User_name,
Rank() over (
partition by organisation_id
order by user_name) rn
From table_name
group by
Organisation_id,
user_name)
Select
Organisation_id,
String_agg(user_name,',') users
From topTen
Where rn <= 10
group by Organisation_id;
organisation_id | users
--------------: | :--------------------------------------
1 | abc,abk,def,ghi,jkl,mno,pqr,rst,ruk,stu
2 | abk,pqr,rst,ruk,stu,vwx
Another alternative which may be useful. If you remove the where and put the following after From topTen you will get all the distinct user_names, 10 per row.
group by Organisation_id,rn/10
order by Organisation_id,rn/10;
db<>fiddle here
Related
Basically each user has a team, and each team has 11 players, so whenever a player scores they earn some points. Now is there a automated way to do this -
As in when there is a update/entry in the USER_TEAM_PLAYERS table, summate the points of all players to the USER_TEAM table for the corresponding user in some column (in this case TEAM_TOTAL column).
I have two tables:
USER_TEAM with columns USER_ID, TEAM_TOTAL
USER_TEAM_PLAYERS with columns PLAYER_NAME, PLAYER_POINTS, USER_ID
Example:
TABLE - USER_TEAM
USER_ID | TEAM_TOTAL
---------------------
1 | 40
2 | 50
TABLE - USER_TEAM_PLAYERS
PLAYER_NAME | PLAYER_POINTS | USER_ID
-------------------------------------
Adam | 10 | 1
Alex | 30 | 1
Botas | 40 | 2
Pepe | 5 | 2
Diogo | 5 | 2
The first table should be only a view of the second one
CREATE VIEW USER_TEAM2 AS
SELECT USER_ID, SUM(PLAYER_POINTS) AS TEAM_TOTAL
FROM USER_TEAM_PLAYERS
GROUP BY USER_ID
ORDER BY USER_ID;
Doing this, you have no duplicate data and a view can be in SELECT, ... like a table.
Nota 1 : I used the name USER_TEAM2 because your first table still exists but you can delete it.
Nota 2 : If you want to have some specific data to the TEAM_TABLE, keep the 2 names, and modifify your view as needed by adding some fields with a JOIN of this first table.
I have performing some queries using PostgreSQL SELECT DISTINCT ON syntax. I would like to have the query return the total number of rows alongside with every result row.
Assume I have a table my_table like the following:
CREATE TABLE my_table(
id int,
my_field text,
id_reference bigint
);
I then have a couple of values:
id | my_field | id_reference
----+----------+--------------
1 | a | 1
1 | b | 2
2 | a | 3
2 | c | 4
3 | x | 5
Basically my_table contains some versioned data. The id_reference is a reference to a global version of the database. Every change to the database will increase the global version number and changes will always add new rows to the tables (instead of updating/deleting values) and they will insert the new version number.
My goal is to perform a query that will only retrieve the latest values in the table, alongside with the total number of rows.
For example, in the above case I would like to retrieve the following output:
| total | id | my_field | id_reference |
+-------+----+----------+--------------+
| 3 | 1 | b | 2 |
+-------+----+----------+--------------+
| 3 | 2 | c | 4 |
+-------+----+----------+--------------+
| 3 | 3 | x | 5 |
+-------+----+----------+--------------+
My attemp is the following:
select distinct on (id)
count(*) over () as total,
*
from my_table
order by id, id_reference desc
This returns almost the correct output, except that total is the number of rows in my_table instead of being the number of rows of the resulting query:
total | id | my_field | id_reference
-------+----+----------+--------------
5 | 1 | b | 2
5 | 2 | c | 4
5 | 3 | x | 5
(3 rows)
As you can see it has 5 instead of the expected 3.
I can fix this by using a subquery and count as an aggregate function:
with my_values as (
select distinct on (id)
*
from my_table
order by id, id_reference desc
)
select count(*) over (), * from my_values
Which produces my expected output.
My question: is there a way to avoid using this subquery and have something similar to count(*) over () return the result I want?
You are looking at my_table 3 ways:
to find the latest id_reference for each id
to find my_field for the latest id_reference for each id
to count the distinct number of ids in the table
I therefore prefer this solution:
select
c.id_count as total,
a.id,
a.my_field,
b.max_id_reference
from
my_table a
join
(
select
id,
max(id_reference) as max_id_reference
from
my_table
group by
id
) b
on
a.id = b.id and
a.id_reference = b.max_id_reference
join
(
select
count(distinct id) as id_count
from
my_table
) c
on true;
This is a bit longer (especially the long thin way I write SQL) but it makes it clear what is happening. If you come back to it in a few months time (somebody usually does) then it will take less time to understand what is going on.
The "on true" at the end is a deliberate cartesian product because there can only ever be exactly one result from the subquery "c" and you do want a cartesian product with that.
There is nothing necessarily wrong with subqueries.
I have a table for the link/relationship between two other tables, a table of customers and a table of groups. a group is made up of one or more customers. The link table is like
APP_ID | GROUP_ID | CUSTOMER_ID
1 | 1 | 123
1 | 1 | 124
1 | 1 | 125
1 | 2 | 123
1 | 2 | 125
2 | 3 | 123
3 | 1 | 123
3 | 1 | 124
3 | 1 | 125
I now have a need, given a list of customer IDs to be able to get the group ID for that list of customer IDs. Group ID may not be unique, the same group ID will contain the same list of customer IDs but this group may exist in more than one app_id.
I'm thinking that
SELECT APP_ID, GROUP_ID, COUNT(CUSTOMER_ID) AS COUNT
FROM GROUP_CUST_REL
WHERE CUSTOMER_ID IN ( <list of ids> )
GROUP BY APP_ID, GROUP_ID
HAVING COUNT(CUSTOMER_ID) = <number of ids in list>
will return me all of the group IDs that contain all of the customer ids in the given list and only those group ids. So for a list of (123,125) only group id 2 would be returned from the above example
I will then have to link with the app table to use its created timestamp to identify the most recent application that the group existed in so that I can then pull the correct/most up to date info from the group table.
Does anyone have any thoughts on whether this is the most efficient way to do this? If there is another quicker/cleaner way I'd appreciate your thoughts.
This smells like a division:
Division sample
Other related stack overflow question
Taking a look at the provided links you'll see the solution to similar issues from relational alegebra's point of view, doesn't seem to be quicker and arguably cleaner.
I didn't look at your solution at first, and when I solved this I turned out to have solved this the same way you did.
Actually, I thought this:
<number of ids in list>
Could be turned into something like this (so that you don't need the extra parameter):
select count(*) from (<list of ids>) as t
But clearly, I was wrong. I'd stay with your current solution if I were you.
Ok this one is realy tricky :D
i have a this table
bills_products:
- bill_id - product_id - action -
| 1 | 4 | add |
| 1 | 5 | add |
| 2 | 4 | remove |
| 2 | 1 | add |
| 3 | 4 | add |
as you can see product with the id 4 was added at bill 1 then removed in bill 2 and added again in bill 3
All Bills belong to a bill_group. But for the simplicity sake let's assume all the bills are in the same group.
Now i need a SQL Query that shows all the products that are currently added at this group.
In this example that would be 5, 1 and 4. If we would remove the bill with id 3 that would be 5 and 1
I've tried to do this with DISTINCT but it's not powerful enough or maybe I'm doing it wrong.
This seems to work in SQL Server at least:
select product_id
from (
select product_id,
sum((case when action='add' then 1 else -1 end)) as number
from bills_products
group by product_id
) as counts
where number > 0
SELECT DISTINCT product_id FROM bills_products WHERE action = 'add';
GSto almost had it, but you have to ORDER BY bill_id DESC to ensure you get the latest records.
SELECT DISTINCT product_id FROM bills_products
WHERE action = 'add'
ORDER BY bill_id DESC;
(P.S. I think most people would say it's a best practice to have a timestamp column on tables like this where you need to be able to know what the "newest" row is. You can't always rely on ids only ascending.)
I have a user table like this
user_id | community_id | registration_date
--------------------------------------------
1 | 1 | 2008-01-01
2 | 1 | 2008-05-01
3 | 2 | 2008-01-28
4 | 2 | 2008-07-22
5 | 3 | 2008-01-11
For each community, I would like to get the time that the 3rd user registered. I can easily do this for a single community using MySql's 'limit' SQL extension. For example, for community with ID=2
select registration_date
from user
order by registration_date
where community_id = 2
limit 2, 1
Alternatively, I can get the date that the first user registered for all communities via:
select community_id, min(registration_date)
from user
group by 1
But I can't figure out how to get the registration date of the 3rd user for all communities in a single SQL statement.
Cheers,
Don
With an inner select:
select
registration_date, community_id
from
user outer
where
user_id IN (
select
user_id
from
user inner
where
inner.community_id = outer.community_id
order by
registration_date
limit 2,1
)
order by registration_date
Selects the set of users where each user is the 3rd user in their community as returned by the limit clause in the inner select.
Is this what you mean?
SELECT registration_date
FROM user
ORDER BY registration_date
LIMIT n
Where n is the user you are concerned about.