为什么使用DAYOFYEAR（DATE）的mysql查询将不同的结果返回DAY（DATE）？

Question

Question as above really.

Just to reiterate I have run two identical queries except for the DAY(DATE) and DAYOFYEAR(DATE) parts which are used in the Select and Group By clauses.

I expected the results to be the same but they differ greatly (DAYOFYEAR returns 344563 results and DAY returns 253637 results). The only explanation I can think of is that January 1st gets grouped with February 1st and so forth because they share the same DAY value. However the result set doesn't seem to show that.

Any confirmation/explanation would be greatly appreciated.

Answer 1

DAYOFMONTH() and DAY() are comparable. today they would both return 16, since today is the 16th of the month, and every month has a day 16. DAYOFYEAR() is a count of how many days since the start of the year. it is something else entirely.