Assign year to months of past 6 months - sql

Question

From below data, how do i assign year in column DS_YEAR where Year is not assigned based on DS_MONTH.
DS_MONTH| DS_DAY| DS_YEAR
--------|---------|--------
Mar | 2 | 2019
Jan | 4 | 2020
Apr | 2 | 07:43
Sep | 1 | 06:00
Jul | 2 | 05:00
Dec | 4 | 2019
Feb | 7 | 2020
Nov | 9 | 2019
From the above data; any data that is between now and past 6 months has a TIME instead of YEAR. However i want to write a query to attach the respective year instead of time.
I have below query which will attach the current year, however in case our data will lie in the months transitioning previous year it wont be accurate.
SELECT
DS_MONTH || '-' || DS_DAY || '-' ||
CASE
WHEN DS_YEAR LIKE '%:%' THEN TO_CHAR(sysdate, 'YYYY')
ELSE DS_YEAR
END dsf
FROM
MY_TABLE
How do i check the month whether it lies in current year or previous year, so that i can assign the correct year?
Example: if today was FEBRUARY. and in my data i have Sep | 1 | 06:00 then my query should return Sep-1-2019
and if today was OCTOBER it should return Sep-1-2020

Answer 1

Is this what you want ?
WITH sampledata (mon, d, yt) AS
(
SELECT 'Mar','2','2019' FROM DUAL UNION
SELECT 'Jan','4','2020' FROM DUAL UNION
SELECT 'Apr','2','07:43' FROM DUAL UNION
SELECT 'Sep','1','06:00' FROM DUAL UNION
SELECT 'Jul','2','05:00' FROM DUAL UNION
SELECT 'Dec','4','2019' FROM DUAL UNION
SELECT 'Feb','7','2020' FROM DUAL UNION
SELECT 'Nov','9','2019' FROM DUAL
),rundate (dt) AS
(
SELECT DATE'2021-05-30' FROM DUAL
)
SELECT s.mon, s.d, s.yt,
CASE WHEN TO_DATE(s.mon||'-'||s.d||'-'|| extract(year from r.dt),'Mon-dd-YYYY') > r.dt THEN TO_DATE(s.mon||'-'||s.d||'-'|| extract(year from ADD_MONTHS(r.dt,-12)),'Mon-dd-YYYY')
ELSE TO_DATE(s.mon||'-'||s.d||'-'|| extract(year from r.dt),'Mon-dd-YYYY')
END
FROM sampledata s CROSS JOIN rundate r
WHERE INSTR(s.yt,':') > 0
UNION
SELECT s.mon, s.d, s.yt, TO_DATE(s.mon||'-'||s.d||'-'|| s.yt,'Mon-dd-YYYY')
FROM sampledata s
WHERE INSTR(s.yt,':') = 0;
UPDATE: Added the 'rundate' CTE so you can test with any date, not just sysdate. Also added the case expression to check ensure the date is in the past.

Answer 2

This is just pseudo code, may require few changes in date/month conversion as per db syntax
SELECT
DS_MONTH || '-' || DS_DAY || '-' ||
CASE
WHEN DS_YEAR LIKE '%:%' and Month(sysdate)>6 THEN TO_CHAR(sysdate, 'YYYY')
WHEN DS_YEAR LIKE '%:%' and Month(cast(DS_MONTH+'1 2015' as datetime)) < 6 THEN TO_CHAR(sysdate, 'YYYY')
WHEN DS_YEAR LIKE '%:%' and Month(cast(DS_MONTH+'1 2015' as datetime)) > 6 THEN TO_CHAR(DATEADD(YEAR, -1, GETDATE()), 'YYYY')
ELSE DS_YEAR
END dsf
FROM
MY_TABLE