Using CURDATE() the wrong way

It has been a while since I wrote on this blog. Basically I had too much on my mind (expanding my department, holidays, etc) to actually write here and I’ll promise to post more regularly from now onwards. 😉

Anyway, as the title already suggests: I found out how you can use CURDATE() in a wrong way. One of the developers in my company asked me to help him out as his code all of a sudden did not work properly anymore. Or even better: it used to process several thousands of rows and all of a sudden it processed none.

I looked at his code snippet and it was quite a long query with a lot of brackets:

SELECT SUM(some_count_col), logdate, loghour FROM logs
WHERE (logdate = CURDATE() AND loghour = HOUR(NOW())
GROUP BY logdate, loghour;

Column wise logdate is of the type DATE and loghour of the type TINYINT.
note that this is, obviously, not the original query, but it is similar

Apart from the fact that his usage of brackets makes the query quite unreadable I was quickly able to simplify the query to this: