Agfdhyk

Changing the question because of a misunderstanding in use case.

Amazon Redshift Query for the following problem statement.

The data structure:

1. id - primary key


2. acc_id - id unique to a loan account (this id will be same for all
   emi's for a particular loan account, this maybe repeated 6 times or
   12 times based on loan tenure which can be 6 months or 12 months
   respectively)


3. status - PAID or UNPAID (the emi's unpaid are followed my unpaid
   emi's only)


4. s_id - just a scheduling id which would be consecutive numbers for a
   a particular loan id


5. due_date - the due date for that particular emi


6. principal - amount that is due

The table:

   id       acc_id status   s_id    due_date            principal

9999957     10003   PAID    102  2018-07-02 12:00:00        4205

9999958     10003   UNPAID  103  2018-08-02 12:00:00        4100

9999959     10003   UNPAID  104  2018-09-02 12:00:00        4266

9999960     10003   UNPAID  105  2018-10-02 12:00:00        4286

9999962     10004   PAID    106  2018-07-02 12:00:00        3200

9999963     10004   PAID    107  2018-08-02 12:00:00        3100

9999964     10004   UNPAID  108  2018-09-02 12:00:00        3266

9999965     10004   UNPAID  109  2018-10-02 12:00:00        3286

The use case -

The unpaid amount becomes delinquent (overdue) after the due_date.

So I need to calculate delinquent amount at the end of every month from the first due_date in this case is 2nd July to last due_date (assume it to be 2nd November which is the current month)

I also need to calculate days past due at the end of that month.

Illustration from the above data:

• From the sample data provided, no EMI is due at the end of July so amount delinquent is 0


• But at the end of August - the id 9999958 is due - as of 31st August
  the amount delinquent is 4100 and days past due is 29 (31st August minus 2nd August)

The catch: I need to calculate this for the loan (acc_id) and not the emi.

To further explain, A first EMI will be 29 days due on 1st month and 59 days due on second month, also second EMI will be 29 days due on second month. But I need this at loan level (acc_id).

The same example continued for 30th september, the acc_id 10003 is due since 2nd August so as of 30th September the due amount is 8366 (4100 + 4266) and DPD (days_past_due) is 59 (29 + 30).

Also acc_id 10004 is due 3100 and DPD is 28 (30th september - 2nd september).

The final output would be something like this:

Month_End   DPD_Band    Amount

2018/08/31  0-29        4100

2018/08/31  30-59       0

2018/08/31  60-89       0

2018/08/31  90+         0

2018/09/30  0-29        3100

2018/09/30  30-59       8366

2018/09/30  60-89       0

2018/09/30  90+         0

Query attempt: DPD bands can be created based on case statements on delinquent days. I need real help in first creating End-of-months and then finding the portfolio level amounts as explained above for different delinquent days.

Edited to be RedShift compatible after the op clarified which RDBMS. (MySQL would need a different answer)

The following creates one record for each month between your first record, and the end of last month.

It then joins on to your unpaid records, and the aggregation chooses which bracket to put the results in to.

WITH

  first_month AS

(

  SELECT LAST_DAY(MIN(due_date)) AS end_date FROM yourTable

),

  months AS

(

  SELECT

    LAST_DAY(ADD_MONTHS(first_month.end_date, s.id))    AS end_date

  FROM

    first_month

  CROSS JOIN

    generate_series(

      1,

      DATEDIFF(month, (SELECT end_date FROM first_month), CURRENT_DATE)

    )

      AS s(id)

),

  monthly_delinquents AS

(

  SELECT

    yourTable.*,

    months.end_date                                        AS month_end_date,

    DATEDIFF(DAY, yourTable.due_date, months.end_date)     AS days_past_due

  FROM

    months

  LEFT JOIN

    yourTable

      ON  yourTable.status   = 'UNPAID'

      AND yourTable.due_date < months.end_date

)

SELECT

  month_end_date,

  SUM(CASE WHEN days_past_due >= 00 AND days_past_due < 30 THEN principal ELSE 0 END)  AS dpd_00_29,

  SUM(CASE WHEN days_past_due >= 30 AND days_past_due < 60 THEN principal ELSE 0 END)  AS dpd_30_59,

  SUM(CASE WHEN days_past_due >= 60 AND days_past_due < 90 THEN principal ELSE 0 END)  AS dpd_60_89,

  SUM(CASE WHEN days_past_due >= 90                        THEN principal ELSE 0 END)  AS dpd_90plus

FROM

  monthly_delinquents

GROUP BY

  month_end_date

ORDER BY

  month_end_date

That said, normally the idea of pivoting things like this is a bad idea. What happens when something is a year past due? It just sits in the 90plus category and never moves. And, if you want to expand it you need to change the query and any other query you ever write that depends on it.

Instead, you could normalise your output...

WITH

  first_month AS

(

  SELECT LAST_DAY(MIN(due_date)) AS end_date FROM yourTable

),

  months AS

(

  SELECT

    LAST_DAY(ADD_MONTHS(first_month.end_date, s.id))    AS end_date

  FROM

    first_month

  CROSS JOIN

    generate_series(

      1,

      DATEDIFF(month, (SELECT end_date FROM first_month), CURRENT_DATE)

    )

      AS s(id)

),

  monthly_delinquents AS

(

  SELECT

    yourTable.*,

    months.end_date                                        AS month_end_date,

    DATEDIFF(DAY, yourTable.due_date, months.end_date)     AS days_past_due

  FROM

    months

  LEFT JOIN

    yourTable

      ON  yourTable.status   = 'UNPAID'

      AND yourTable.due_date < months.end_date

)

SELECT

  month_end_date,

  (days_past_due / 30) * 30   AS days_past_due_band,

  SUM(principal)              AS total_principal,

  COUNT(*)                    AS total_rows

FROM

  monthly_delinquents

GROUP BY

  month_end_date,

  (days_past_due / 30) * 30

ORDER BY

  month_end_date,

  (days_past_due / 30) * 30