I have a table containing data that has a column named id that looks like below:
id
value 1
value 2
value 3
1
244
550
1000
1
251
551
700
1
540
60
1200
...
...
...
...
2
19
744
2000
2
10
903
100
2
44
231
600
2
120
910
1100
...
...
...
...
I want to take 50 sample rows per id that exists but if less than 50 exist for the group to simply take the entire set of data points.
For example I would like a maximum 50 data points randomly selected from id = 1, id = 2 etc...
I cannot find any previous questions similar to this but have tried taking a stab at at least logically working through the solution where I could iterate and union all queries by id and limit to 50:
SELECT * FROM (SELECT * FROM schema.table AS tbl WHERE tbl.id = X LIMIT 50) UNION ALL;
But it's obvious that you cannot use this type of solution because UNION ALL requires aggregating outputs from one id to the next and I do not have a list of id values to use in place of X in tbl.id = X.
Is there a way to accomplish this by gathering that list of unique id values and union all results or is there a more optimal way this could be done?
If you want to select a random sample for each id, then you need to randomize the rows somehow. Here is a way to do it:
select * from (
select *, row_number() over (partition by id order by random()) as u
from schema.table
) as a
where u <= 50;
Example (limiting to 3, and some row number for each id so you can see the selection randomness):
setup
DROP TABLE IF EXISTS foo;
CREATE TABLE foo
(
id int,
value1 int,
idrow int
);
INSERT INTO foo
select 1 as id, (1000*random())::int as value1, generate_series(1, 100) as idrow
union all
select 2 as id, (1000*random())::int as value1, generate_series(1, 100) as idrow
union all
select 3 as id, (1000*random())::int as value1, generate_series(1, 100) as idrow;
Selection
select * from (
select *, row_number() over (partition by id order by random()) as u
from foo
) as a
where u <= 3;
Output:
id
value1
idrow
u
1
542
6
1
1
24
86
2
1
155
74
3
2
505
95
1
2
100
46
2
2
422
33
3
3
966
88
1
3
747
89
2
3
664
19
3
In case you are looking to get 50 (or less) from each group of IDs then you can use windowing -
From question - "I want to take 50 sample rows per id that exists but if less than 50 exist for the group to simply take the entire set of data points."
Query -
with data as (
select row_number() over (partition by id order by random()) rn,
* from table_name)
select * from data where rn<=50 order by id;
Fiddle.
Your description of trying to get the UNION ALL without specifying all the branches ahead of time is aiming for a LATERAL join. And that is one way to solve the problem. But unless you have a table of all distinct ids, you would have to compute one on the fly. For example (using the same fiddle as Pankaj used):
with uniq as (select distinct id from test)
select foo.* from uniq cross join lateral
(select * from test where test.id=uniq.id order by random() limit 3) foo
This could be either slower or faster than the Window Function method, depending on your system and your data and your indexes. In my hands, it was quite a bit faster even with the need to dynamically compute the list of distinct ids.
From the DB (Postgresql) I want to get the percentage per month (of all months) of stock items with a certain condition. So the total of the whole month is 100% and per condition it would be a percentage of that. I'm trying all kinds of 'partition by' queries, but i quite can't get it right.
In the example there would be an extra column and on each row there would be the percentage of that month. So the value for the new column for the first row it would be 25/506*100.
Right now I have and works is:
select to_char(created_at, 'YYYY-MM') as maand, count(si.id) as aantal,
case
when condition_id=1 then 'Nieuw'
when condition_id=2 then 'Als nieuw'
when condition_id=3 then 'Goed'
when condition_id=4 then 'Redelijk'
when condition_id=5 then 'Matig'
else 'Onbepaald'
end
from stock_items si
group by maand, condition_id
order by maand desc, condition_id asc
maand
aantal
case
new column
2022-01
25
Nieuw
25/506*100
2022-01
234
Als nieuw
234/506*100
2022-01
127
Goed
127/506*100
2022-01
16
Redelijk
16/506*100
2022-01
104
Matig
104/506*100
2021-12
456
Nieuw
other month
I hope it's all clear. Thanks!
I got what I wanted. To realise i want it a little different, but this is the answer to my question.
select
to_char(created_at, 'YYYY-MM') as maand,
count(id) as aantal,
round((count(id) / (sum(count(id)) over (partition by to_char(created_at, 'YYYY-MM'))) * 100), 2) as percentage,
case
when condition_id=1 then 'Nieuw'
when condition_id=2 then 'Als nieuw'
when condition_id=3 then 'Goed'
when condition_id=4 then 'Redelijk'
when condition_id=5 then 'Matig'
else 'Onbepaald'
end
from stock_items
group by maand, condition_id
order by maand desc, condition_id asc
just warp it with CTE.
with a as (
select to_char(created_at, 'YYYY-MM') as maand, count(si.id) as aantal,
case
when condition_id=1 then 'Nieuw'
when condition_id=2 then 'Als nieuw'
when condition_id=3 then 'Goed'
when condition_id=4 then 'Redelijk'
when condition_id=5 then 'Matig'
else 'Onbepaald'
end as case
from stock_items si
group by maand, condition_id
order by maand desc, condition_id asc)
select a.*, aantal * 100 / sum(aantal) over (PARTITION BY maand) as anntal_rate from a;
/* some characters so the edit is accepted */
SELECT max(salary),
(SELECT MAX(SALARY) FROM EMPLOYEE
WHERE SALARY NOT IN(SELECT MAX(SALARY) FROM EMPLOYEE)) as 2ND_MAX_SALARY;
This is giving me the error: FROM keyword not found where expected
You want the top 2 of your table ordered by one of the columns (the FETCH NEXT clause is available from Oracle 12c R1)
SELECT Salary FROM Employee ORDER BY Salary DESC LIMIT 2
FETCH NEXT 2 ROWS ONLY;
Use
SELECT Salary FROM Employee ORDER BY Salary DESC LIMIT 2
FETCH NEXT 2 ROWS WITH TIES;
if you want to return all employees that have the 1st or 2nd highest salary: There might only be one highest salary amount in the company, but more than one employee who gets that amount. Those rows are the ties.
If you're on Oracle database version lower than 12c, rank analytic function might help.
For sample rows:
SQL> select * from employee order by salary desc;
ENAME SALARY
---------- ----------
KING 5000 --> highest salary
FORD 3000 --> Ford and Scott "share" the 2nd
SCOTT 3000 --> highest salary
JONES 2975
BLAKE 2850
CLARK 2450
ALLEN 1600
TURNER 1500
MILLER 1300
WARD 1250
MARTIN 1250
ADAMS 1100
JAMES 950
SMITH 800
14 rows selected.
In a subquery (or a CTE, as I did), calculate rank for each salary and then, in the main query, select rows that rank as to top salaries:
SQL> with temp as
2 (select ename,
3 salary,
4 rank() over (order by salary desc) rnk
5 from employee
6 )
7 select ename, salary
8 from temp
9 where rnk <= 2
10 order by rnk desc;
ENAME SALARY
---------- ----------
SCOTT 3000
FORD 3000
KING 5000
SQL>
SELECT MAX(salary) AS max_salary,
(SELECT MAX(salary)
FROM employee
WHERE salary NOT IN (SELECT MAX(salary)
FROM employee
)
) AS 2nD_max_salary
FROM employee;
I have a table with the following entries in them
id price quantity
1. 10 75
2. 10 75
3. 10 -150
4. 10 75
5. 10 -75
What I need to do is to update each row with a number that is the number of times the running total has been 0. In the above example, the cumulative totals would be
id. cum_total
1. 750
2. 1500
3. 0
4. 750
5. 0
Desired result
id price quantity seq
1. 10 75 1
2. 10 75 1
3. 10 -150 1
4. 10 75 2
5. 10 -75 2
I'm now lost in a spiral of CTEs and window functions and figured I'd ask the experts.
Thanks in advance :-)
Here is one option using analytic functions:
WITH cte AS (
SELECT *, CASE WHEN SUM(price*quantity) OVER (ORDER BY id) = 0 THEN 1 ELSE 0 END AS price_sum
FROM yourTable
),
cte2 AS (
SELECT *, LAG(price_sum, 1, 0) OVER (ORDER BY id) price_sum_lag
FROM cte
)
SELECT id, price, quantity, 1 + SUM(price_sum_lag) OVER (ORDER BY id) cumulative_total
FROM cte2
ORDER BY id;
Demo
You may try running each CTE in succession to see how the logic is working.
With window functions:
SELECT id, price, quantity,
coalesce(
sum(CASE WHEN iszero THEN 1 ELSE 0 END)
OVER (ORDER BY id
ROWS BETWEEN UNBOUNDED PRECEDING AND 1 PRECEDING),
0
) + 1 AS batch
FROM (SELECT id, price, quantity,
sum(price * quantity) OVER (ORDER BY id) = 0 AS iszero
FROM mytable) AS subq;
I am using SQL Server 2014. I have a table like this
create table revenue (id varchar(2), trasdate date, revenue int);
insert into revenue(id, trasdate, revenue)
values ('aa', '2018/09/01', 1234.5),
('aa' , '2018/08/04', 450),
('aa', '2018/07/03',500),
('aa', '2018/06/04',600),
('ab', '2018/09/01', 1234.5),
('ab' , '2018/08/04', 450),
('ab', '2018/07/03',500),
('ab', '2018/06/04',600),
('ab', '2018/05/03', 200),
('ab', '2018/04/02', 150),
('ab', '2018/03/01', 350),
('ab', '2018/02/05', 700),
('aa', '2018/01/07', 400)
;
I am preparing a SQL query to create a SSRS report. I want to calculate a past 3 month average for current and every past 3rd month with result like below. As we are in month of September right now. The result should show something like this:
**id Period Revenue_3Mon**
aa March-May 233
aa June-Aug 516
ab March-May 233
ab June-Aug 516
Though I can figure out about the Period column. I was mainly focussing on getting the Revenue_3Mon. So I initially tried with the below query after some googling. But this query throws an error as incorrect syntax near 'rows' and if I remove rows from the query then it throws an error as Incorrect syntax near the keyword 'between'. And incorrect syntax near i.
select i.id,i.mon,
avg([i.mon_revenue]) over (partition by i.id, i.mon order by [i.id],
[i.mon] rows between 3 preceding and 1 preceding row) as revenue_3mon --
-- using 3 preceding and 1 preceding row you exclude the current row
from (select a.id, month(a.trasdate) as mon,
sum(a.revenue) as mon_revenue
from revenue a
group by a.id, month(a.trasdate)) i
group by i.id, i.mon
order by i.id,i.mon;
After few efforts, I gave up on this query and came up with new solution which was a bit close to my expectation (after lots of trial and errors).
Declare #count as int;
declare #max as int;
set #count = 4
declare #temp as table (id varchar(2), monthoftrasdate int, revenue int,
[3monavg] int);
SET #MAX = (SELECT distinct MAX(a.ROWNUM) FROM (SELECT id, month(trasdate)
as mon, SUM(revenue) TotalRevenue,
-- sum(revenue) as mon_revenue,
ROW_NUMBER() OVER(PARTITION BY ID ORDER BY MONTH(TRASDATE)) AS ROWNUM
FROM revenue
GROUP BY ID, MONTH(TRASDATE)
) A GROUP BY A.ID);
while (#count <= #max )
begin
WITH CTE AS (
SELECT id, month(trasdate) as mon, SUM(revenue) TotalRevenue,
-- sum(revenue) as mon_revenue,
ROW_NUMBER() OVER(PARTITION BY ID ORDER BY MONTH(TRASDATE)) AS
ROWNUM
FROM revenue
GROUP BY ID, MONTH(TRASDATE)
)
insert into #temp
SELECT A.ID,A.MON, a.TotalRevenue
,( SELECT avg(b.TotalRevenue) as avgrev
FROM CTE B
WHERE B.ROWNUM BETWEEN A.ROWNUM-3 AND A.ROWNUM-1
AND A.ID = B.ID --AND A.mon = B.mon
--and b.ROWNUM < a.ROWNUM
and (a.mon > 3 and a.ROWNUM > 3)
GROUP BY B.id
) AS REVENUE_3MON
FROM CTE A
set #count = #count + 1
end
select distinct a.* from #temp a
The reason I had to use 'distinct' is because the query was showing duplicate records for every id and every month. So far the result shows like below
id MonthofTrasdate Revenue 3MonAvg
aa 1 400 NULL
aa 2 700 NULL
aa 3 350 NULL
aa 4 150 483
aa 5 200 400
aa 6 600 233
aa 7 500 316
aa 8 450 433
aa 9 1234 516
ab 1 400 NULL
ab 2 700 NULL
ab 3 350 NULL
ab 4 150 483
ab 5 200 400
ab 6 600 233
ab 7 500 316
ab 8 450 433
ab 9 1234 516
This pulls out past 3 month average for every month. But i will just manipulate the rest on SSRS the way i want it.
As currently my table has no data for previous year. This works for me showing the appropriate result for next couple of months for now. But my concern is when I have to show my boss for next year Jan, Feb and March then it should be able to pull also for these months as well like Oct-Dec (Previous year), Nov-Jan and Dec - Feb. I am struggling to figure out the proper way to put this in my query.
Can you please help me out with this query? And also let me know what is wrong with my former query.
Problems with your first attempt:
You enclosed some of the aliases and column names in square brackets like [i.mon_revenue]. There is no need for square brackets, but if you want to use them, you have to break them up at the dot: [i].[mon_revenue].
In your window function expression, there is one row too many (in the end).
Window functions are applied at the very end (after the rest of the respective query), so you also have to include i.mon_revenue in your GROUP BY clause of the outer query.
Knowing that the inner query will produce one row per id and mon, there will never be preceding rows in an id-mon partition. Therefore, you must not partition by both, but only by id.
To simplify the query after resolving the issues: ordering by a partition column generally makes no sense, and since - as already mentioned - the inner query returns unique id-mon combinations, you don't have to group by these in the outer query. Looking at that query, we see that the outer query just directly selects and uses the values from the inner query, which makes a separation in two queries unneccessary. So, in fact, you wanted to perform the following query, which will produce the rolling 3-month average (I added the monthly TotalRevenue as well):
SELECT id, MONTH(trasdate) AS mon, SUM(revenue) AS TotalRevenue,
AVG(SUM(revenue)) OVER (PARTITION BY id ORDER BY MONTH(trasdate) ROWS BETWEEN 3 PRECEDING AND 1 PRECEDING) AS revenue_3mon
FROM revenue
GROUP BY id, MONTH(trasdate)
ORDER BY id, MONTH(trasdate);
Suggestions on your second attempt:
When calculating the #MAX value, you rely on the fact that each id has revenues for the same number of months. Are you sure?
The code inside the WHILE loop does not depend on #count, so it will add the same data into the #temp table multiple times, which is probably the reason why you thought you needed a DISTINCT. Therfore: No need for the variables, no need for a loop and a #temp, no need for DISTINCT.
The conditions A.mon > 3 and A.rownum > 3 are redundant with your current data. In general, I guess, you don't want to explicitly excluse the months from January to March, so A.mon > 3 should be removed. A.rownum > 3 could be removed, too, unless you really don't want to see a 3-month average when there are only 2 preceding months or less.
As the subquery for the average is restricted to only one id, there's no need for a GROUP BY.
Since the ROW_NUMBER function doesn't care about gaps in the months, I suggest to use a different numbering function, for example DATEDIFF(month, MAX(trasdate), GETDATE()) AS mnum. Of course, the comparison in the WHERE clause of the subquery then has to be changed to B.mnum BETWEEN A.mnum+1 AND A.mnum+3.
So, your second attempt can be reduced to this, which will produce the same result as the above, at least with your sample data, where no gaps in the months exist:
WITH CTE AS (
SELECT id, MONTH(trasdate) AS mon, SUM(revenue) AS TotalRevenue,
DATEDIFF(month, MAX(trasdate), GETDATE()) AS mnum
FROM revenue
GROUP BY id, MONTH(trasdate)
)
SELECT id, mon, TotalRevenue
, (SELECT AVG(B.TotalRevenue)
FROM CTE B
WHERE B.mnum BETWEEN A.mnum+1 AND A.mnum+3
AND A.id = B.id
) AS revenue_3mon
FROM CTE A
ORDER BY id, mnum DESC;
Now, guess what, an expression like my mnum using DATEDIFF increases by one every month as we move to the past, regardless of a change of years, so this might be useful for grouping as well, whether you want to (or can?) use Window functions or not:
With OVER()
SELECT id, MONTH(MIN(trasdate)) AS mon, YEAR(MIN(trasdate)) AS yr, SUM(revenue) AS TotalRevenue,
AVG(SUM(revenue)) OVER (PARTITION BY id ORDER BY MIN(trasdate) ROWS BETWEEN 3 PRECEDING AND 1 PRECEDING) AS revenue_3mon
FROM revenue
GROUP BY id, DATEDIFF(month, trasdate, GETDATE())
ORDER BY id, DATEDIFF(month, trasdate, GETDATE()) DESC;
Without OVER()
WITH CTE AS (
SELECT id, MIN(trasdate) AS min_dt, SUM(revenue) AS TotalRevenue,
DATEDIFF(month, trasdate, GETDATE()) AS mnum
FROM revenue
GROUP BY id, DATEDIFF(month, trasdate, GETDATE())
)
SELECT id, MONTH(min_dt) AS mon, YEAR(min_dt) AS yr, TotalRevenue
, (SELECT AVG(B.TotalRevenue)
FROM CTE B
WHERE B.mnum BETWEEN A.mnum+1 AND A.mnum+3
AND A.id = B.id
) AS revenue_3mon
FROM CTE A
ORDER BY id, mnum DESC;
Both queries allow for retrieving the minimum and maximum date for each period (including month and year).
If you instead wanted what you originally posted under The result should show something like this (just grouping by previous 3-months intervals), you just would have to group your original revenue table by id and (DATEDIFF(month, trasdate, GETDATE())-1)/3 (filtering WHERE DATEDIFF(month, trasdate, GETDATE()) > 0). If so, this kind of grouping and aggregation could, of course, be done also by the Report Server.
I think this should do what you want:
select r.*,
avg(r.mon_revenue) over (partition by r.id
order by r.mon_min
rows between 3 preceding and 1 preceding row
) as revenue_3mon
-- using 3 preceding and 1 preceding row you exclude the current row
from (select r.id, month(r.trasdate) as mon,
min(r.trasdate) as mon_min,
sum(r.revenue) as mon_revenue
from revenue r
group by r.id, year(r.trasdate), month(r.trasdate)
) 4
order by r.id, r.mon, r.mon_min;
Notes:
I fixed the code so it recognizes years as well as dates.
The expression [i.mon_revenue] is not a valid column reference (in your case). You have no column with the name "i.mon_revenue" (with the . in the name).
I changed the column alias to r to match the table.
I added a date column for each month to make it easier to express the ordering.
The outer group by is not necessary.
There are several syntax errors in your code. This should give you what you need. The inner query is the important bit but hopefully this will be enough to get you on your way.
I switch our the temp table for variable and changed the revenue column to not be INT as you have decimal values in there but other than that your original sample table is unchanged
DECLARE #revenue table (id varchar(2), trasdate date, revenue float)
insert into #revenue(id, trasdate, revenue)
values ('aa', '2018/09/01', 1234.5),
('aa' , '2018/08/04', 450),
('aa', '2018/07/03',500),
('aa', '2018/06/04',600),
('ab', '2018/09/01', 1234.5),
('ab' , '2018/08/04', 450),
('ab', '2018/07/03',500),
('ab', '2018/06/04',600),
('ab', '2018/05/03', 200),
('ab', '2018/04/02', 150),
('ab', '2018/03/01', 350),
('ab', '2018/02/05', 700),
('aa', '2018/01/07', 400)
SELECT
*
FROM
(
SELECT
*
, MONTH(trasdate) as MonthNumber
, AVG(revenue) OVER (PARTITION BY id
ORDER BY
id
, MONTH(trasdate) ROWS BETWEEN 3 PRECEDING AND 1 PRECEDING) as ThreeMonthAvg
FROM #revenue
) a
WHERE MONTH(GETDATE()) - MonthNumber IN (0, 3, 6, 9)
This gives the following results
aa 2018-06-04 600 6 400
aa 2018-09-01 1234.5 9 516.666666666667
ab 2018-03-01 350 3 700
ab 2018-06-04 600 6 233.333333333333
ab 2018-09-01 1234.5 9 516.666666666667