Postgresql - SQL set of filters

Tomy
July 16, 2023
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0 votes
2 Answers

I am facing with a little challenge. I know that this kind of challenge should be solved by using python but I have decided to do it with SQL. And I am looking for little help as I am kind of beginner 🙂

I have set of data with 4 columns.

first column represent account ID (receivable)
second column represent date of transaction
3rd column represent amounts
4th column represent account ID which has sent the transaction to account ID receivable

First I have done is that I have set kind of subtable which will group account ID (receivable). The reson why is that I want to apply set of filters against group of records from particular account ID receivable.. I have set this query like this:

SELECT t1.account_receivable,t1.datum,t1.amount,t1.account_payable
FROM python_table as t1
WHERE t1.account_receivable IN (
    SELECT t2.account_receivable
    FROM python_table as t2
    GROUP BY 1                  )

and now I want to do this crazy condition for records..
I want records only which has at least 3 consecutive months sent from same account ID of 4th column. There can not be sent more than 1 transaction in same month othervise I do not want to display this. interval for days must be maximum 5 from the lowest day of group (consecutive months)

here is the one group of data for 1 account ID (receivable). I have tried to explain as much as possible what I am trying to achieve… I tried almost everything but not able to solve this one,.. Asking myself is it even possible in SQL with so many conditions?

61441   2014-04-28  102 45437871
61441   2014-04-28  15346   45437871
61441   2014-05-16  98  306658150
**61441 2014-04-28  711 323671229
61441   2014-05-23  694 323671229
61441   2014-06-25  701 323671229
61441   2014-07-25  702 323671229
61441   2014-08-25  694 323671229
61441   2014-09-25  644 323671229**
**61441 2014-06-09  3697    342058995   this set will not match condition as interval for day
61441   2014-07-04  3692    342058995   from lowest to highest is more than 5 days
61441   2014-08-06  3665    342058995
61441   2014-09-10  3672    342058995**
61441   2014-06-10  8409    357368301
61441   2014-04-24  4136    412899724
**61441 2014-04-28  1261    440261807
61441   2014-05-23  1271    440261807
61441   2014-06-25  1267    440261807
61441   2014-07-25  1259    440261807
61441   2014-08-25  1274    440261807
61441   2014-09-25  1120    440261807**
61441   2014-06-19  141 441460477
61441   2014-08-06  314 518735975
**61441 2014-04-01  17032   547166056
61441   2014-05-02  45773   547166056
61441   2014-06-02  17821   547166056
61441   2014-07-01  17445   547166056
61441   2014-08-01  25562   547166056
61441   2014-09-02  17459   547166056**
61441   2014-09-05  157 686201636
61441   2014-09-19  126 686201636
**61441 2014-04-14  7233    762490320  This will not match condition as it has 3 transactions in
61441   2014-05-19  9703    762490320  same month
61441   2014-06-16  8875    762490320
61441   2014-07-14  8274    762490320
61441   2014-07-18  1436    762490320
61441   2014-07-28  841 762490320
61441   2014-08-15  11008   762490320
61441   2014-09-16  8334    762490320**
61441   2014-05-16  340 838201881
61441   2014-05-21  2480    838201881
61441   2014-07-14  295 838201881
61441   2014-07-14  933 838201881
61441   2014-08-25  1696    838201881
61441   2014-08-25  849 838201881
61441   2014-04-28  2011    842644517
61441   2014-09-22  8295    842644517
61441   2014-07-09  35  982718888

Tags: postgresql

Answers

This can be achieved with window functions.

The result from the below query differs from yours in that payments from 762490320 to 61441 had a three-month block that met the other criteria from April 2014 to June 2014 before it was interrupted by the triple payment in July.

with lines as (
  select *, date_trunc('month', datum)::date as year_month,
         extract('day' from datum) as day_of_month
    from python_table
), double_taps as (
  select *, 
         count(*) 
           over (partition by account_receivable, account_payable, year_month)
           as monthly_count
    from lines
), consecutive_island_breaks as (
  select *, 
         case 
           when year_month - interval '1 month' = lag(year_month) over w then 0
           else 1
         end as new_group
    from double_taps
   where monthly_count = 1
  window w as (partition by account_receivable, account_payable order by datum) 
), islands as (
  select *,
         sum(new_group) over w as island_number
    from consecutive_island_breaks
  window w as (partition by account_receivable, account_payable 
                   order by datum)
), island_sizes as (
  select *,
         count(*) over w as island_size,
         max(day_of_month) over w - min(day_of_month) over w as day_range
    from islands
  window w as (partition by account_receivable, account_payable, island_number)
)
select * 
  from island_sizes
 where island_size >= 3
   and day_range <= 5;

Working fiddle

first_value(datum) OVER (PARTITION BY account_receivable,
        account_payable ORDER BY datum) AS first_datum

to solve the " interval for days must be maximum 5 from the lowest day of group (consecutive months)".

count(*) OVER (PARTITION BY  
 account_receivable,account_payable,date_trunc('month', datum)) AS cnt_txn_mon,

to solve "There can not be sent more than 1 transaction in same month othervise I do not want to display this"

"I want records only which has at least 3 consecutive months":
means that count of (lead(date_trunc(‘month’, datum),1) = date_trunc(‘month’, datum) + interval ‘1 month’ is true) >= 2.

demo: https://dbfiddle.uk/uwXO0tDe
query:


WITH cte AS 
(
    SELECT
        datum,
        account_receivable,
        account_payable,
        /* for the consective month computation */
        coalesce(lead(date_trunc('month', datum)::date, 1) 
            OVER (PARTITION BY account_receivable, account_payable ORDER BY datum)
            ,date_trunc('month', datum)::date) 
        = (date_trunc('month', datum) + interval '1 month')::date AS is_next_month,
        /*for max 1 txns*/
        count(*) OVER (
            PARTITION BY account_receivable,account_payable,date_trunc('month', datum)) AS cnt_txn_mon,
        /*for maximum 5 from the lowest day of group*/
        first_value(datum) OVER (
                PARTITION BY account_receivable,account_payable ORDER BY datum) AS first_datum
    FROM  python_table
),cte1 AS 
(
    SELECT
        datum,
        account_receivable,
        account_payable,
        cnt_txn_mon,
        /*ignore date order, means in a group, there is a 3 consective month is fine */
        count(is_next_month) FILTER (WHERE is_next_month) OVER (PARTITION BY account_receivable,
            account_payable) AS cnt_mon_gaps,
        /*for maximum 5 from the lowest day of group*/
        abs(date_trunc('month', first_datum)::date - first_datum) <= 5
        OR abs((date_trunc('month', first_datum) + interval '1 month')::date - first_datum) <= 5 AS date_near_month
    FROM    cte        
    WHERE   cnt_txn_mon = 1
        
)
SELECT *
FROM      cte1
WHERE     cnt_mon_gaps >= 2 AND date_near_month
ORDER BY  account_payable,datum;

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Postgresql – SQL set of filters

Answers