Get the last 4 weeks prior to current week of and the same 4 weeks of last year - sql

Question

I have a list of date, fiscal week, and fiscal year:
DATE_VALUE FISCAL_WEEK FISCAL_YEAR_VALUE
14-Dec-20 51 2020
15-Dec-20 51 2020
16-Dec-20 51 2020
17-Dec-20 51 2020
18-Dec-20 51 2020
19-Dec-20 51 2020
20-Dec-20 51 2020
21-Dec-20 52 2020
22-Dec-20 52 2020
23-Dec-20 52 2020
24-Dec-20 52 2020
25-Dec-20 52 2020
26-Dec-20 52 2020
27-Dec-20 52 2020
28-Dec-20 1 2021
29-Dec-20 1 2021
30-Dec-20 1 2021
31-Dec-20 1 2021
1-Jan-21 1 2021
2-Jan-21 1 2021
3-Jan-21 1 2021
4-Jan-21 2 2021
5-Jan-21 2 2021
6-Jan-21 2 2021
7-Jan-21 2 2021
8-Jan-21 2 2021
9-Jan-21 2 2021
10-Jan-21 2 2021
11-Jan-21 3 2021
12-Jan-21 3 2021
13-Jan-21 3 2021
14-Jan-21 3 2021
15-Jan-21 3 2021
16-Jan-21 3 2021
17-Jan-21 3 2021
18-Jan-21 4 2021
19-Jan-21 4 2021
20-Jan-21 4 2021
21-Jan-21 4 2021
22-Jan-21 4 2021
23-Jan-21 4 2021
24-Jan-21 4 2021
20-Dec-21 52 2021
21-Dec-21 52 2021
22-Dec-21 52 2021
23-Dec-21 52 2021
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
1-Jan-22 53 2021
2-Jan-22 53 2021
3-Jan-22 1 2022
4-Jan-22 1 2022
5-Jan-22 1 2022
6-Jan-22 1 2022
7-Jan-22 1 2022
8-Jan-22 1 2022
9-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
15-Jan-22 2 2022
16-Jan-22 2 2022
17-Jan-22 3 2022
18-Jan-22 3 2022
19-Jan-22 3 2022
20-Jan-22 3 2022
21-Jan-22 3 2022
22-Jan-22 3 2022
23-Jan-22 3 2022
24-Jan-22 4 2022
25-Jan-22 4 2022
26-Jan-22 4 2022
27-Jan-22 4 2022
28-Jan-22 4 2022
29-Jan-22 4 2022
30-Jan-22 4 2022
I want to pull the last 4 weeks prior to the current week AND the same 4 weeks of the year before. Please see example 1. This works fine when all 4 weeks are within the same year. But when it comes to the beginning of a year when 1 or more weeks are in the current year but the other are in the previous year, I am not able to get the desired output below:
FISCAL_YEAR_VALUE FISCAL_WEEK
2020 51
2020 52
2021 2
2021 1
2021 52
2021 53
2022 1
2022 2
The code I have is below. I am using the date of 21-JAN-22 as an example:
SELECT
FISCAL_YEAR_VALUE,
FISCAL_WEEK
FROM TABLE_NAME
WHERE FISCAL_YEAR_VALUE IN (SELECT *
FROM (WITH T AS (
SELECT DISTINCT FISCAL_YEAR_VALUE
FROM TABLE_NAME
WHERE TRUNC(DATE_VALUE) <= TRUNC(TO_DATE('21-JAN-22'))--TEST DATE
ORDER BY FISCAL_YEAR_VALUE DESC
FETCH NEXT 2 ROWS ONLY
)
SELECT FISCAL_YEAR_VALUE
FROM T ORDER BY FISCAL_YEAR_VALUE
)
)
AND FISCAL_WEEK IN (SELECT *
FROM (WITH T AS (
SELECT DISTINCT FISCAL_WEEK, FISCAL_YEAR_VALUE
FROM TABLE_NAME
WHERE TRUNC(DATE_VALUE) <= TRUNC(TO_DATE('21-JAN-22'))--TEST DATE
ORDER BY FISCAL_YEAR_VALUE DESC, FISCAL_WEEK DESC
OFFSET 1 ROWS
FETCH NEXT 4 ROWS ONLY
)
SELECT FISCAL_WEEK
FROM T ORDER BY FISCAL_YEAR_VALUE, FISCAL_WEEK
)
)
GROUP BY FISCAL_YEAR_VALUE, FISCAL_WEEK
ORDER BY FISCAL_YEAR_VALUE, FISCAL_WEEK
Output of the code is:
FISCAL_YEAR_VALUE FISCAL_WEEK
2021 2
2021 1
2021 52
2021 53
2022 1
2022 2
As you can see, the last 2 weeks of year 2020 are not included. Please see example 2. How can I also include this exception in the code to make it dynamic? Any help would be greatly appreciated!

Answer 1

To find the values this year, you can use:
SELECT DISTINCT fiscal_year_value, fiscal_week
FROM table_name
WHERE date_value < TRUNC(SYSDATE, 'IW')
AND date_value >= TRUNC(SYSDATE, 'IW') - INTERVAL '28' DAY
To find the values from the previous year, you can find the maximum fiscal week from this year and subtract 1 from the year and then use that to find the upper bound of the date_value for last fiscal year and, given that can use a similar range for last year:
WITH this_year (fiscal_year_value, fiscal_week) AS (
SELECT fiscal_year_value, fiscal_week
FROM table_name
WHERE date_value < TRUNC(SYSDATE, 'IW')
AND date_value >= TRUNC(SYSDATE, 'IW') - INTERVAL '28' DAY
),
max_last_year (max_date_value) AS (
SELECT MAX(date_value) + INTERVAL '1' DAY
FROM table_name
WHERE (fiscal_year_value, fiscal_week) IN (
SELECT fiscal_year_value - 1, fiscal_week
FROM this_year
ORDER BY fiscal_year_value DESC, fiscal_week DESC
FETCH FIRST ROW ONLY
)
)
SELECT fiscal_year_value, fiscal_week
FROM this_year
UNION
SELECT t.fiscal_year_value, t.fiscal_week
FROM table_name t
INNER JOIN max_last_year m
ON ( t.date_value < m.max_date_value
AND t.date_value >= m.max_date_value - INTERVAL '28' DAY);
Which, for the sample data:
Create Table table_name(DATE_VALUE DATE, FISCAL_WEEK INT, FISCAL_YEAR_VALUE INT);
INSERT INTO table_name (date_value, fiscal_week, fiscal_year_value)
SELECT DATE '2019-12-30' + LEVEL - 1, CEIL(LEVEL/7), 2020
FROM DUAL
CONNECT BY LEVEL <= 7 * 52
UNION ALL
SELECT DATE '2020-12-28' + LEVEL - 1, CEIL(LEVEL/7), 2021
FROM DUAL
CONNECT BY LEVEL <= 7 * 53
UNION ALL
SELECT DATE '2022-01-03' + LEVEL - 1, CEIL(LEVEL/7), 2022
FROM DUAL
CONNECT BY LEVEL <= 7 * 52;
Outputs:
FISCAL_YEAR_VALUE
FISCAL_WEEK
2022
38
2022
39
2022
40
2022
41
2021
38
2021
39
2021
40
2021
41
And if today's date was 2022-01-01, would output:
FISCAL_YEAR_VALUE
FISCAL_WEEK
2021
52
2021
53
2022
1
2022
2
2020
51
2020
52
2021
1
2021
2
There may be a simpler method but without any knowledge of how you calculate a fiscal year that is not immediately possible.
fiddle