Date arithmetics
From SQLZoo
Group by day of the week (using arithmetic).
schema:gisq
We can use modular arithmetic to calculate the day of the week.
We happen to know that 20 May 1962 was a Sunday. We calculate the number of days from that day and take mod 7 value. This tells us the day of the week: 0 is Sunday, 1 is Monday...
SELECT MOD(wk - TO_DATE('1962-05-20','YYYY-MM-DD'),7),
COUNT(song)
FROM gisq.totp
GROUP BY MOD(wk - TO_DATE('1962-05-20','YYYY-MM-DD'),7)
