I have a query, which returns a simple list of numbers:
SELECT unnest(c) FROM t ORDER BY f LIMIT 10;
And it goes like
1
1
3
4
2
3
5
1
5
6
3
2
I want to keep the result unique, but also preserve order:
1
3
2
4
5
6
select distinct(id) from (select ...) as c;
does not work, beacuse it uses HashAggregate, which breaks order (and processes all rows to return just 10?). I tried GROUP BY, it also uses HashAggregate the whole table(?) and then sort and return 10 required rows.
Is it possible to do it effectively on DB size? Or should I just read rows from my first query in my application and do the stream filtering?
with ordinality is your friend to preserve the order.
select val
from unnest('{1,1,3,4,2,3,5,1,5,6,3,2}'::int[]) with ordinality t(val, ord)
group by val
order by min(ord); -- the first time that this item appeared
val
1
3
4
2
5
6
Or it may make sense to define this function:
create function arr_unique(arr anyarray)
returns anyarray language sql immutable as
$$
select array_agg(val order by ord)
from
(
select val, min(ord) ord
from unnest(arr) with ordinality t(val, ord)
group by val
) t;
$$;
select elem
from (
select
elem, elem_no, row_no, row_number() over (partition by elem order by row_no) as occurence_no
from (
select elem, elem_no, row_number() over () as row_no from t, unnest(c) WITH ORDINALITY a(elem, elem_no)
) A
) B
where occurence_no = 1
order by row_no
Related
While trying to map some data to a table, I wanted to obtain the ID of a table and its modulo respect the total rows in the same table. For example, given this table:
id
--
1
3
10
12
I would like this result:
id | mod
---+----
1 | 1 <- 1 mod 4
3 | 3 <- 3 mod 4
10 | 2 <- 10 mod 4
12 | 0 <- 12 mod 4
Is there an easy way to achieve this dynamically (as in, not counting the rows on before hand or doing it in an atomic way)?
So far I've tried something like this:
SELECT t1.id, t1.id % COUNT(t1.id) mod FROM tbl t1, tbl t2 GROUP BY t1.id;
This works but you must have the GROUP BY and tbl t2 as otherwise it returns 0 for the mod column which makes sense because I think it works by multiplying the table by itself so each ID gets a full set of the table. I guess for small enough tables this is ok but I can see how this becomes problematic for larger tables.
Edit: Found another hack-ish way:
WITH total AS (
SELECT COUNT(*) cnt FROM tbl
)
SELECT t1.id, t1.id % t2.cnt mod FROM tbl t1, total t2
It similar to the previous query but it "collapses" the multiplication to a single row with the previous count.
You can use COUNT() window function:
SELECT id,
id % COUNT(*) OVER () mod
FROM tbl;
I'm sure that the optimizer is smart enough to calculate the result of the window function only once.
See the demo.
I am working on peoplesoft. I have a requirement where I have to update the column value in a sequence ordered based on some ID.
For eg.
CA24100001648- 1
CA24100001648- 2
CA24100001664- 1
CA24100001664- 2
CA24100001664- 3
CA24100001664- 4
CA24100001664- 5
CA24100001664- 6
But, I am getting '1' as the value for all the rows on updating.
Here is my query, can anyone please help out on this.
UPDATE PS_UC_CA_CONT_STG C
SET C.CONTRACT_LINE_NUM2 = ( SELECT row_number() over(PARTITION BY D.CONTRACT_NUM
order by D.CONTRACT_NUM)
FROM PS_UC_CA_HDR_STG D
WHERE C.CONTRACT_NUM=D.CONTRACT_NUM );
Thanksenter image description here
update emp a
set comm =
(with cnt as ( select deptno,empno,row_number() over (partition by deptno order by deptno) rn from emp)
select c.rn from cnt c where c.empno=a.empno)
I have a table looks like,
x y
1 2
2 null
3 null
1 null
11 null
I want to fill the null value by conducting a rolling
function to apply y_{i+1}=y_{i}+x_{i+1} with sql as simple as possible (inplace)
so the expected result
x y
1 2
2 4
3 7
1 8
11 19
implement in postgresql. I may encapsulate it in a window function, but the implementation of custom function seems always complex
WITH RECURSIVE t AS (
select x, y, 1 as rank from my_table where y is not null
UNION ALL
SELECT A.x, A.x+ t.y y , t.rank + 1 rank FROM t
inner join
(select row_number() over () rank, x, y from my_table ) A
on t.rank+1 = A.rank
)
SELECT x,y FROM t;
You can iterate over rows using a recursive CTE. But in order to do so, you need a way to jump from row to row. Here's an example using an ID column:
; with recursive cte as
(
select id
, y
from Table1
where id = 1
union all
select cur.id
, prev.y + cur.x
from Table1 cur
join cte prev
on cur.id = prev.id + 1
)
select *
from cte
;
You can see the query at SQL Fiddle. If you don't have an ID column, but you do have another way to order the rows, you can use row_number() to get an ID:
; with recursive sorted as
(
-- Specify your ordering here. This example sorts by the dt column.
select row_number() over (order by dt) as id
, *
from Table1
)
, cte as
(
select id
, y
from sorted
where id = 1
union all
select cur.id
, prev.y + cur.x
from sorted cur
join cte prev
on cur.id = prev.id + 1
)
select *
from cte
;
Here's the SQL Fiddle link.
I have been banging my head trying to come up with the correct logic (SQL Server 2012) needed to achieve something I would imagine would be fairly routine but I have been unable to find any examples of this anywhere. Basically, I have 3 columns in a table: product, flag, value. It is possible for a product to be listed multiple times within the table but only once with a unique flag (i.e. product1 can have flag1 or flag2 with different/identical but there will never be 2 records with product1 and flag1 and different/identical values).
The flag represents a pre-defined value (1,2,3,4) and the intention behind this field is to be able to assign a unique mathematical equation based on the value of the flag. The end result would yield a single product, the unique flag, and a new cumulative total based on the mathematical equation output. For instance, let's say product1 was listed 4 times with flag values of flag1, flag2, flag3, flag4 (see below):
Product-----Flag-----Value
Product1----Flag1----1.00
Product1----Flag2----3.00
Product1----Flag3----5.00
Product1----Flag4----7.00
Product-----Flag-----Value
Product1----Flag1----1.00 (flag1 value)
Product1----Flag2----4.00 (flag1+flag2 value)
Product1----Flag3----6.00 (flag1+flag3 value)
Product1----Flag4----10.00 (flag2+flag4 value)
Flag1 is defined as add flag1 only. Flag2 is defined as add flag1 and flag2. Flag 3 is defined as add flag1 and flag 3. Flag 4 is defined as add flag2 and flag4. the new output would be product1 listed four times with flag values of flag1, flag2, flag3, flag4 but new values as flag1, flag1_flag2, flag1+flag3, flag2+flag4.
I have tried to apply the logic via a case statement but I can't figure out how to traverse all the products for each condition and I have tried to go with a running totals solution but I am not sure how to incorporate the flag condition into it so it only performs a running total for when those conditions are true. Any assistance and/or article to help get me going down the right path would be greatly appreciated.
While I'm not sure I fully understand your question I think this might be what you want. For this to work it assumes flag1 is always present when flags 1 through 3 are and that flag2 is present when flag4 is.
;with cte as (
select
product,
max(case when flag = 'Flag1' then Value end) as f1Value,
max(case when flag = 'Flag2' then Value end) as f2Value,
max(case when flag = 'Flag3' then Value end) as f3Value,
max(case when flag = 'Flag4' then Value end) as f4Value
from flags group by Product
)
select
flags.Product,
flags.Flag,
flags.Value as "Org. value",
case flag
when 'Flag1' then f1Value
when 'Flag2' then f1Value + f2Value
when 'Flag3' then f1Value + f3Value
when 'Flag4' then f2Value + f4Value
else flags.Value -- take the present value when flag is not Flag1-4
end as "New value"
from flags
inner join cte on flags.Product = cte.Product
Take a look at this Sample SQL Fiddle to see it in action.
You can join a table to itself, and pick the conditions appropriately:
SELECT p1.product,p1.Flag,p1.Value + COALESCE(p2.Value,0)
FROM
Products p1
left join
Products p2
on
p1.Product = p2.Product and
p2.Flag = CASE p1.Flag
--1 doesn't need a previous value
WHEN 2 THEN 1
WHEN 3 THEN 1
WHEN 4 THEN 2
END
I assumed and tried on Range values.
CREATE TABLE #tmp (Product VARCHAR(10), flag VARCHAR(10),value numeric(13,2))
GO
INSERT INTO #tmp
SELECT 'Product1' , 'Flag1',1
UNION
SELECT 'Product1' , 'Flag2',3
UNION
SELECT 'Product1' , 'Flag3',5
UNION
SELECT 'Product1' , 'Flag4',7
GO
;WITH cte
AS
(
SELECT row_number () OVER(
ORDER BY flag) 'row',*
FROM #tmp
)
SELECT *,value 'RT'
FROM cte
WHERE row = 1
UNION
SELECT * ,(
SELECT cte.value
FROM cte
WHERE row = 1
) + value 'RT'
FROM cte
WHERE row BETWEEN 2
AND 3
UNION
SELECT * ,(
SELECT cte.value
FROM cte
WHERE row =2
) + value 'RT'
FROM cte
WHERE row >3
GO
DROP TABLE #tmp
I have one main table called Event_log which contains all of the records that I need for this query. Within this table there is one column that I'm calling "Grp". To simplify things, assume that there are only two possible values for this Grp: A and B. So now we have one table, Event_log, with one column "Grp" and one more column called "Actual Date". Lastly I want to add one more Flag column to this table, which works as follows.
First, I order all of the records in descending order by date as demonstrated below. Then, I want to flag each Group "A" row with a 1 or a 0. For all "A" rows, if the previous record (earlier in date) = "B" row then I want to flag 1. Otherwise flag a 0. So this initial table looks like this before setting this flag:
Actual Date Grp Flag
1-29-13 A
12-27-12 B
12-26-12 B
12-23-12 A
12-22-12 A
But after these calculations are done, it should look like this:
Actual Date Grp Flag
1-29-13 A 1
12-27-12 B NULL
12-26-12 B NULL
12-23-12 A 0
12-22-12 A 0
How can I do this? This is simpler to describe than it is to query!
You can use something like:
select el.ActualDate
, el.Grp
, Flag = case
when el.grp = 'B' then null
when prev.grp = 'B' then 1
else 0
end
from Event_log el
outer apply
(
select top 1 prev.grp
from Event_log prev
where el.ActualDate > prev.ActualDate
order by prev.ActualDate desc
) prev
order by el.ActualDate desc
SQL Fiddle with demo.
Try this
;with cte as
(
SELECT CAST('01-29-13' As DateTime) ActualDate,'A' Grp
UNION ALL SELECT '12-27-12','B'
UNION ALL SELECT '12-26-12','B'
UNION ALL SELECT '12-23-12','A'
UNION ALL SELECT '12-22-12','A'
)
, CTE2 as
(
SELECT *, ROW_NUMBER() OVER (order by actualdate desc) rn
FROM cte
)
SELECT a.*,
case
when A.Grp = 'A' THEN
CASE WHEN b.Grp = 'B' THEN 1 ELSE 0 END
ELSE NULL
END Flag
from cte2 a
LEFT OUTER JOIN CTE2 b on a.rn + 1 = b.rn