Get the last 4 weeks prior to current week - sql

Question

I have a table that has DATE_VALUE, FISCAL_WEEK, FISCAL_YEAR
DATE_VALUE FISCAL_WEEK FISCAL_YEAR
24-DEC-21 52 2021
25-DEC-21 52 2021
26-DEC-21 52 2021
27-DEC-21 53 2021
28-DEC-21 53 2021
29-DEC-21 53 2021
30-DEC-21 53 2021
31-DEC-21 53 2021
01-JAN-22 53 2021
02-JAN-22 53 2021
03-JAN-22 1 2022
04-JAN-22 1 2022
05-JAN-22 1 2022
06-JAN-22 1 2022
07-JAN-22 1 2022
08-JAN-22 1 2022
09-JAN-22 1 2022
10-JAN-22 2 2022
11-JAN-22 2 2022
12-JAN-22 2 2022
13-JAN-22 2 2022
14-JAN-22 2 2022
The table goes on for the entire FY 2021 & 2022
I want to get the last 4 fiscal weeks (FW) prior to the current week. Let's assume this week is FW20 FY2022, I am able to get this result:
FISCAL_WEEK FISCAL_YEAR
16 2022
17 2022
18 2022
19 2022
The code used to return the above output is:
SELECT
*
FROM
(
WITH t AS (
SELECT
fiscal_week - 1 lastweek,
fiscal_week - 5 week_x,
fiscal_year
FROM
TABLE
WHERE
Trunc(date_value) = Trunc(sysdate)
)
SELECT
DISTINCT fiscal_week,
t.fiscal_year
FROM
TABLE
OUTER JOIN t ON fiscal_week <> week_x
WHERE
to_char(fiscal_week) BETWEEN lastweek - 4
AND lastweek
ORDER BY
fiscal_week
)
But if the current week was FW04 FY2022, the code above is not able to return this desired output.
FISCAL_WEEK FISCAL_YEAR
53 2021
1 2022
2 2022
3 2022
Similarly, if the current was FY03 FY2022, I want the output to be:
FISCAL_WEEK FISCAL_YEAR
52 2021
53 2021
1 2022
2 2022
How do I need to write the code to get this output? Maybe the case statement could work but I'd like to see if there's any other workaround? Any help would be appreciated.
Thank you!

Answer 1

You may put the condition on the date value not the week to get the required output, then use OFFSET 1 to skip the current week and fetch the next 4 rows only. Try the following:
WITH T AS
(
SELECT DISTINCT fiscal_week, fiscal_year
FROM TABLE_NAME
WHERE Trunc(date_value) <= Trunc(SYSDATE)
ORDER BY fiscal_year DESC, fiscal_week DESC
OFFSET 1 ROWS
FETCH NEXT 4 ROWS ONLY
)
SELECT fiscal_week, fiscal_year
FROM T ORDER BY fiscal_year, fiscal_week
See a demo.

Answer 2

Don't use the FISCAL_WEEK and FISCAL_YEAR columns; just use the DATE column and compare it to a range based on the start of the ISO week:
SELECT DISTINCT fiscal_week, fiscal_year
FROM table_name
WHERE "DATE" < TRUNC(SYSDATE, 'IW')
AND "DATE" >= TRUNC(SYSDATE, 'IW') - INTERVAL '28' DAY
ORDER BY fiscal_year, fiscal_week;
Which, for the sample data:
Create Table table_name("DATE", FISCAL_WEEK, FISCAL_YEAR) AS
SELECT DATE '2021-12-24', 52, 2021 FROM DUAL UNION ALL
SELECT DATE '2021-12-25', 52, 2021 FROM DUAL UNION ALL
SELECT DATE '2021-12-26', 52, 2021 FROM DUAL UNION ALL
SELECT DATE '2021-12-27', 53, 2021 FROM DUAL UNION ALL
SELECT DATE '2021-12-28', 53, 2021 FROM DUAL UNION ALL
SELECT DATE '2021-12-29', 53, 2021 FROM DUAL UNION ALL
SELECT DATE '2021-12-30', 53, 2021 FROM DUAL UNION ALL
SELECT DATE '2021-12-31', 53, 2021 FROM DUAL UNION ALL
SELECT DATE '2022-01-01', 53, 2021 FROM DUAL UNION ALL
SELECT DATE '2022-01-02', 53, 2021 FROM DUAL UNION ALL
SELECT DATE '2022-01-03', 1, 2022 FROM DUAL UNION ALL
SELECT DATE '2022-01-04', 1, 2022 FROM DUAL UNION ALL
SELECT DATE '2022-01-05', 1, 2022 FROM DUAL UNION ALL
SELECT DATE '2022-01-06', 1, 2022 FROM DUAL UNION ALL
SELECT DATE '2022-01-07', 1, 2022 FROM DUAL UNION ALL
SELECT DATE '2022-01-08', 1, 2022 FROM DUAL UNION ALL
SELECT DATE '2022-01-09', 1, 2022 FROM DUAL UNION ALL
SELECT DATE '2022-01-10', 2, 2022 FROM DUAL UNION ALL
SELECT DATE '2022-01-11', 2, 2022 FROM DUAL UNION ALL
SELECT DATE '2022-01-12', 2, 2022 FROM DUAL UNION ALL
SELECT DATE '2022-01-13', 2, 2022 FROM DUAL UNION ALL
SELECT DATE '2022-01-14', 2, 2022 FROM DUAL UNION ALL
SELECT DATE '2022-02-14', 6, 2022 FROM DUAL;
If SYSDATE was 2022-01-17, would output:
FISCAL_WEEK
FISCAL_YEAR
52
2021
53
2021
1
2022
2
2022
fiddle