I'm trying to select the group_items of the top N largest groups with the same grouping_attribute from a table, and doing something like this:
SELECT grouping_attribute, group_item,
ROW_NUMBER() OVER (PARTITION BY grouping_attribute ORDER BY ???) AS rn
FROM a_table
WHERE rn < N;
But I don't know what to put in the ORDER BY clause to make it happen. I'm trying to order the rows by the size of their corresponding partitions. COUNT(*) doesn't run. I was hoping there was some way to refer to the size of the partition, but I can't find anything.
If I understand correctly, you want count(*) not row_number(). Use count(*) to get the size of the partitions and then order the resulting rows afterwards. For instance:
SELECT a.*
FROM (SELECT grouping_attribute, group_item,
COUNT(*) over (partition by grouping_attribute) as cnt
FROM a_table
) a
ORDER BY cnt DESC;
Related
Hopefully, someone can help me...
I'm trying to get the last two values from a row_number() window function. Let's say my results contain row numbers up to 6, for example. How would it be possible to get the rows where the row number is 5 and 6?
Let me know if it can be done with another window function or in another way.
Kind regards,
Using QUALIFY:
SELECT *
FROM tab
QUALIFY ROW_NUMBER() OVER(ORDER BY ... DESC) <= 2;
This approach could be further extended to get two rows per each partition:
SELECT *
FROM tab
QUALIFY ROW_NUMBER() OVER(PARTITION BY ... ORDER BY ... DESC) <= 2;
You can use top with order by desc like:
select top 2 row_number() over([partition by] [order by]) as rn
from table
order by rn desc
I'd say #Shmiel is the formal and elegant way, just in case, would be the same as :
WITH CTE AS
(SELECT product,
user_id,
ROW_NUMBER() OVER (PARTITION BY user_id order by product desc)
as RN
FROM Mytable)
SELECT product, user_id
FROM CTE
WHERE RN < 3;
You will use order by [order_condition] with "desc". And then you will use RN(row number) to select as many rows as you want
I have a table with multiple rows of the same member id. I need only distinct rows based on 2 unique columns
Ex: there are 100 different customers, the table has 1000 rows because every customer has multiple cities and segments assigned to him.
I need 100 distinct rows for these customers depending on a unique segment and city combination. There is no specific requirement for this combination, just the first from the table is fine.
So, currently the table is somewhat like this,
Hope this helps.
use row_number()
select * from (select *,row_number() over(partition by memberid order by sales) rn
from table_name
) a where a.rn=1
Handy sql-server top(1) with ties syntax for that
select top(1) with ties t.*
from table_name t
order by row_number() over(partition by memberid order by sales)
As you have no paticular requirement for which exactly row to select, any column will do at order by, it can be null as well
select top(1) with ties t.*
from table_name t
order by row_number() over(partition by memberid order by (select null))
The simplest way to do this is to use the ROW_NUMBER() OVER(GROUP BY...) syntax. You have no need to use an order by, since you want an arbitrary row, but only one, for each member.
Since you need only the expected data, and not the Row_Number value, make sure that you detail the fields returned, like below:
SELECT
MemberId,
city,
segment,
sales
FROM (
SELECT *
ROW_NUMBER() OVER (GROUP BY MemberId) as Seq
FROM [Status]
) src
WHERE Seq = 1
how to add to the query max(o.Acct)-1 rows. I need to visualize the last two o.Acct rows. My query is currently showing only the max(o.Acct)
SELECT Max(o.Acct) AS [MaxAcct],o.ObjectID,o.Opertype
FROM Operations o
GROUP By o.ObjectID,o.Opertype
If you want to see the last two rows (per group), you're better off using ROW_NUMBER() rather than GROUP BY.
SELECT
*
FROM
(
SELECT
*,
ROW_NUMBER() OVER (PARTITION BY ObjectID,
Opertype
ORDER BY Acct DESC
)
AS sequence_id
FROM
Operations
)
sortedOperations
WHERE
sequence_id <= 2
ORDER BY
ObjectID,
Opertype,
Acct
If you want the last two of something, I'm thinking order by and top. Something like this:
select top (2) o.*
from Operations o
order by o.acct desc;
Suppose we have an accounts table along with the already given values
I want to find the type of account with second highest number of accounts. In this case, result should be 'FD'. In case their is a contention for second highest count I need all those types in the result.
I'm not getting any idea of how to do it. I've found numerous posts for finding second highest values, say salary, in a table. But not for second highest COUNT.
This can be done using cte's. Get the counts for each type as the first step. Then use dense_rank (to get multiple rows with same counts in case of ties) to get the rank of rows by type based on counts. Finally, select the second ranked row.
with counts as (
select type, count(*) cnt
from yourtable
group by type)
, ranks as (
select type, dense_rank() over(order by cnt desc) rnk
from counts)
select type
from ranks
where rnk = 2;
One option is to use row_number() (or dense_rank(), depending on what "second" means when there are ties):
select a.*
from (select a.type, count(*) as cnt,
row_number() over (order by count(*) desc) as seqnum
from accounta a
group by a.type
) a
where seqnum = 2;
In Oracle 12c+, you can use offset/fetch:
select a.type, count(*) as cnt
from accounta a
group by a.type
order by count(*) desc
offset 1
fetch first 1 row only
How can I add a sequential row number to a query that is using order by?
Let say I have a request in this form :
SELECT row_number() over(), data
FROM myTable
ORDER BY data
This will produce the desired result as rows are ordered by "data", but the row numbers are also ordered by data. I understand this is normal as my row number is generated before the order by, but how can I generate this row number after the order by?
I did try to use a subquery like this :
SELECT row_number() over(ORDER BY data), *
FROM
(
SELECT data
FROM myTable
ORDER BY data
) As t1
As shown here, but DB2 doesn't seem to support this syntax SELECT ..., * FROM
Thanks !
You also need to use alaias name before '*'
SELECT row_number() over(ORDER BY data), t1.*
FROM
(
SELECT data
FROM myTable
ORDER BY data
) As t1
You don't need a subquery to do this,
SELECT data , row_number() over(ORDER BY data) as rn
FROM myTable
ORDER BY data