MySQL Get data by previous quarter - mysql

Question

I am trying to find the last entry for the previous years quarter.
All I can access is year i.e 2021 and quarter i.e 1
Here is the data in my database:
id
name
start
end
16
April 2021
2021-04-01
2021-04-30
15
March 2021
2021-03-01
2021-03-31
14
February 2021
2021-02-01
2021-02-28
57
November 2020
2020-11-01
2020-11-30
55
October 2020
2020-10-01
2020-10-31
29
September 2020
2020-09-01
2020-09-30
27
July 2020
2020-07-01
2020-07-31
24
April 2020
2020-04-01
2020-04-30
23
March 2020
2020-03-01
2020-03-31
22
February 2020
2020-02-01
2020-02-29
21
January 2020
2020-01-01
2020-01-31
Using the MySQL quarter function I can get it to print out the quarter as an integer in another column:
SET #given_year = 2021;
SET #given_quarter = 1;
SELECT
id, name, start, end, QUARTER(end) as "Q"
FROM
submissions
id
name
start
end
Q
16
April 2021
2021-04-01
2021-04-30
2
15
March 2021
2021-03-01
2021-03-31
1
14
February 2021
2021-02-01
2021-02-28
1
57
November 2020
2020-11-01
2020-11-30
4
55
October 2020
2020-10-01
2020-10-31
4
29
September 2020
2020-09-01
2020-09-30
3
27
July 2020
2020-07-01
2020-07-31
3
24
April 2020
2020-04-01
2020-04-30
2
23
March 2020
2020-03-01
2020-03-31
1
22
February 2020
2020-02-01
2020-02-29
1
21
January 2020
2020-01-01
2020-01-31
1
I tried using WHERE and LIKE but it is returning 0 rows:
SELECT * FROM (
SELECT
id, name, start, end, QUARTER(end) as "Q"
FROM
submissions as s
) AS vs
WHERE
vs.end
LIKE
#given_year
AND
vs.Q < #given_quarter
I also need to account for the possibility that there may be no rows this year and I need to find the previous year.
For example with these two rows, if I was passed the year 2021 and quarter 1 I would need to return November of the previous year and a different quarter.
id
name
start
end
Q
14
February
2021
2021-02-01
2021-02-28
57
November
2020
2020-11-01
2020-11-30

Answer 1

If I understand correctly, you want all the rows from the quarter in the data before a given quarter. You can filter and use dense_rank():
select s.*
from (select s.*,
dense_rank() over (order by year(start) desc, quarter(start) desc) as seqnum
from submissions s
where year(start) < #given_year or
(year(start) = #given_year and quarter(start) < #given_quarter)
) s
where seqnum = 1;
The above returns all rows from the previous quarter (which is what I thought you wanted). If you want only one row:
select s.*
from submissions s
where year(start) < #given_year or
(year(start) = #given_year and quarter(start) < #given_quarter)
order by start desc
limit 1;