I have a query SELECT * from TABLE which gives the result as below table:
Expected column is as below:
I want to frame a new column like whenever we get the value as 0 then the number should be incremented by 1. I tried DENSE_RANK() , ROW_NUMBER() but couldn't get the exact result which mentioned. Is that possible in PostgreSQL.
Try This:
select name, value,
sum(case when value=0 then 1 else 0 end) over (order by "sno")
from (
select row_number() over() as "sno",* from example
) tab
DEMO
NOTE: Please note that there is no guaranteed that you will get same output always due no ordering field in your raw data.
So Better approach is to add some field in your view output by which it can be ordered and run the query like below:(assuming you have a ID field)
select
name,
value,
sum(case when value=0 then 1 else 0 end) over (order by id)
from example
DEMO
Related
I have the following sample table
And the output should be the first date (for each id) when cum_rev reaches the 100 mark.
I tried the following, because I taught with group bz trick and the where condition i will only get the first occurrence of value higher than 100.
SELECT id
,pd
,cum_rev
FROM (
SELECT id
,pd
,rev
,SUM(rev) OVER (
PARTITION BY id
ORDER BY pd
) AS cum_rev
FROM tab1
)
WHERE cum_rev >= 100
GROUP BY id
But it is not working, and I get the following error. And also when I add an alias is not helping
ERROR: subquery in FROM must have an alias LINE 4: FROM (
^ HINT: For example, FROM (SELECT ...) [AS] foo.
So the desired output is:
2 2015-04-02 135.70
3 2015-07-03 102.36
Do I need another approach? Can anyone help?
Thanks
demo:db<>fiddle
SELECT
id, total
FROM (
SELECT
*,
SUM(rev) OVER (PARTITION BY id ORDER BY pd) - rev as prev_total,
SUM(rev) OVER (PARTITION BY id ORDER BY pd) as total
FROM tab1
) s
WHERE total >= 100 AND prev_total < 100
You can use the cumulative SUM() window function for each id group (partition). To find the first which goes over a threshold you need to check the previous value for being under the threshold while the current one meets it.
PS: You got the error because your subquery is missing an alias. In my example its just s
I have a table named raw_data with the following data
as You can see id 1 and 2 share the same values in field desa, kecamatan and kabupaten, also id 3,4,5.
So basically I want to select all rows that is not followed by the same previous values. expected result would be:
I know it's easy to do this in any programming languages such as PHP, but I need this in postgresql. is this doable? Thanks in Advance.
Assuming higher id denotes latest row, if a row with same all three columns is present not together and you don't want to filter it out as it doesn't have same values as previous row (order by id or created_date), then you can make use of analytic lag() function:
select *
from (
select
t.*,
case
when desa = lag(desa) over (order by id)
and kecamatan = lag(kecamatan) over (order by id)
and kabupaten = lag(kabupaten) over (order by id)
then 0 else 1
end flag
from your_table t
) t where flag = 1;
I have a table test in postgresql 9.3 having fields ID,sch_item_number and dup_test.Schema name is tablet. I need to update dup_test on certain conditions i.e. If there are only unique sch_item_number then the dup_test will be 'diff'.Incase of duplicate sch_item_number, the first record of that duplicate sch_item_number must be 'diff' and the rest should be 'same'. Please find the attached screenshot. I have shared the fiddle too. http://sqlfiddle.com/#!9/1b135c
Sch_item_number=Item
You can try below sql:
select
a.item,
(Case a.sno when 1 then 'diff' else 'same' end) as dup_test
from (
select ROW_NUMBER() OVER (PARTITION BY Item ORDER BY Item) as Sno, * from
table
)a
group by a.item,
(Case a.sno when 1 then 'diff' else 'same' end)
Suppose I have a table with quantity column.
CREATE TABLE transfers (
user_id integer,
quantity integer,
created timestamp default now()
);
I'd like to iteratively go thru a partition using window functions, but access the output rows, not the input table rows.
To access the input table rows I could do something like this:
SELECT LAG(quantity, 1, 0)
OVER (PARTITION BY user_id ORDER BY created)
FROM transfers;
I need to access the previous output row to calculate the next output row. How can i access the lag row in the output? Something like:
CREATE VIEW balance AS
SELECT LAG(balance.total, 1, 0) + quantity AS total
OVER (PARTITION BY user_id ORDER BY created)
FROM transfers;
Edit
This is a minimal example to support the question of how to access the previous output row within a window partition. I don't actually want a sum.
It seems you attempt to calculate a running sum. Luckily that's just what Sum() window function does:
WITH transfers AS(
SELECT i, random()-0.3 AS quantity FROM generate_series(1,100) as i
)
SELECT i, quantity, sum(quantity) OVER (ORDER BY i) from transfers;
I guess, looking at the question, that the only you need is to calculate a cumulative sum.
To calculate a cumulative summ use this query:
SELECT *,
SUM( CASE WHEN quantity IS NULL THEN 0 ELSE quantity END)
OVER ( PARTITION BY user_id ORDER BY created
ROWS BETWEEN unbounded preceding AND current row
) As cumulative_sum
FROM transfers
ORDER BY user_id, created
;
But if you want more complex calculations, especially containing some conditions (decisions) that depend on a result from prevoius row, then you need a recursive approach.
I have a field that is similar to a MAC address in that the first part is a group ID and the second part is a serial number. My field is alphanumeric and 5 digits in length, and the first 3 are the group ID.
I need a query that gives me all distinct group IDs and the first serial number lexicographically. Here is sample data:
ID
-----
X4MCC
X4MEE
X4MFF
V21DD
8Z6BB
8Z6FF
Desired Output:
ID
-----
X4MCC
V21DD
8Z6BB
I know I can do SELECT DISTINCT SUBSTRING(ID, 1, 3) but I don't know how to get the first one lexicographically.
Another way which seems to have the same cost as the query by gbn:
SELECT MIN(id)
FROM your_table
GROUP BY SUBSTRING(id, 1, 3);
SELECT
ID
FROM
(
SELECT
ID,
ROW_NUMBER() OVER (PARTITION BY SUBSTRING(ID, 1, 3) ORDER BY ID) AS rn
FROM MyTable
) oops
WHERE
rn = 1