SQL query to get the data as of 31/03 of past three years - sql

Question

I have created the above query which give me the Bonus tagged to the person as of sysdate.
select
person_number ,
peef.effective_start_Date,
peef.value Amount
from
per_all_people_f papf,
pay_element_entries_f peef
where
papf.person_id = peef.person_id
and PEEF.element_name in ('Bonus')
and sysdate between peef.effective_start_Date and peef.effective_end_Date
I want to tweak the above query to get the Amount for past three years as of 31/3 i.e. instead of sysdate as of 31/3/2021, 31/03/2020,31/03/2019
Output like -
Person_NUMBER effective_start_Date current_Amount 2021_AMOUNT 2020_AMOUNT 2019_AMOUNT
How can i tweak the same query and change the sysdate condition to look for data for past three years as well for the 2021_amount, 2020_amount and 2019_amount column

Answer 1

You can move the last line to the SELECT list as conditionals such as
SELECT person_number, peef.effective_start_Date,
peef.value AS current_amount,
CASE WHEN date'2021-03-31' BETWEEN peef.effective_start_Date AND peef.effective_end_Date
THEN peef.value
END AS 2021_amount,
CASE WHEN date'2020-03-31' BETWEEN peef.effective_start_Date AND peef.effective_end_Date
THEN peef.value
END AS 2020_amount,
CASE WHEN date'2019-03-31' BETWEEN peef.effective_start_Date AND peef.effective_end_Date
THEN peef.value
END AS 2019_amount
FROM per_all_people_f papf
JOIN pay_element_entries_f peef
ON peef.person_id = papf.person_id
WHERE peef.element_name = 'Bonus'
in order to get the currently displayed result, but in this case there will be multiple lines with NULL values for amount columns. I suspect that you need to get aggregated results in order to show the summed up amounts, then consider adding SUM() aggregation such as
SELECT person_number, peef.effective_start_Date,
SUM( peef.value ) AS current_amount,
SUM( CASE WHEN date'2021-03-31' BETWEEN peef.effective_start_Date AND peef.effective_end_Date
THEN peef.value
END ) AS 2021_amount,
SUM( CASE WHEN date'2020-03-31' BETWEEN peef.effective_start_Date AND peef.effective_end_Date
THEN peef.value
END ) AS 2020_amount,
SUM( CASE WHEN date'2019-03-31' BETWEEN peef.effective_start_Date AND peef.effective_end_Date
THEN peef.value
END ) AS 2019_amount
FROM per_all_people_f papf
JOIN pay_element_entries_f peef
ON peef.person_id = papf.person_id
WHERE peef.element_name = 'Bonus'
GROUP BY person_number, peef.effective_start_Date