User Attendance Date Year and Month Wise - sql

Question

I've a requirement to show user attendance year and month wise. Here is a sample
how it would look - Very basic:
Year - Jan - Feb
2018 - 26 - 20
2019 - 20 - 22
The data is retrieved from a single table and I tried the following query
to do so:
SELECT EXTRACT(YEAR FROM M.DATE) "YEAR",
COUNT(CASE WHEN EXTRACT(MONTH FROM M.DATE) = '1' THEN M.Id ELSE '-' END) "Jan",
COUNT(CASE WHEN EXTRACT(MONTH FROM M.DATE) = '2' THEN M.Id ELSE '-' END) "Feb"
FROM TABLE m
WHERE M.STATUS = 'P' AND M.Id = '12345678'
GROUP BY EXTRACT(YEAR FROM M.DATE) ORDER BY EXTRACT(YEAR FROM M.DATE);
Unfortunately this doesn't return the expected data, instead it shows the yearly
attendance of a user for each month as follows:
Year - Jan - Feb
2018 - 292 - 292
2019 - 100 - 100
Did I miss something here? Any ideas would be appreciated.

Answer 1

Try this-
SELECT EXTRACT(YEAR FROM M.DATE) "YEAR",
COUNT(CASE WHEN EXTRACT(MONTH FROM M.DATE) = '1' THEN M.Id ELSE NULL END) "Jan",
COUNT(CASE WHEN EXTRACT(MONTH FROM M.DATE) = '2' THEN M.Id ELSE NULL END) "Feb"
FROM TABLE m
WHERE M.STATUS = 'P' AND M.Id = '12345678'
GROUP BY EXTRACT(YEAR FROM M.DATE) ORDER BY EXTRACT(YEAR FROM M.DATE);
OR-
SELECT EXTRACT(YEAR FROM M.DATE) "YEAR",
SUM(CASE WHEN EXTRACT(MONTH FROM M.DATE) = '1' THEN 1 ELSE 0 END) "Jan",
SUM(CASE WHEN EXTRACT(MONTH FROM M.DATE) = '2' THEN 1 ELSE 0 END) "Feb"
FROM TABLE m
WHERE M.STATUS = 'P' AND M.Id = '12345678'
GROUP BY EXTRACT(YEAR FROM M.DATE) ORDER BY EXTRACT(YEAR FROM M.DATE);

Answer 2

I prefer using SUM() for this. But more importantly, your code is mixing types. EXTRACT() returns a number so the comparison should be to a number. I recommend:
SELECT EXTRACT(YEAR FROM M.DATE) as "YEAR",
SUM(CASE WHEN EXTRACT(MONTH FROM M.DATE) = 1 THEN 1 ELSE 0 END) as "Jan",
SUM(CASE WHEN EXTRACT(MONTH FROM M.DATE) = 2 THEN 1 ELSE 0 END) as "Feb"
FROM TABLE m
WHERE M.STATUS = 'P' AND
M.Id = 12345678 -- I am guessing that `id` is also a number
GROUP BY EXTRACT(YEAR FROM M.DATE)
ORDER BY EXTRACT(YEAR FROM M.DATE);
You should be careful mixing types. Conversions can impede the ability of the optimizer to find the best query plan.