Re: To store or calculate on the spot?

[Rick James]

Oops, this was a typo: LEFT(10, datetime, 10)

mysql> SELECT LEFT(NOW(), 10), LEFT(NOW(), 7);
+-----------------+----------------+
| LEFT(NOW(), 10) | LEFT(NOW(), 7) |
+-----------------+----------------+
| 2011-07-24      | 2011-07        |
+-----------------+----------------+

Those are ways to turn a date or a datetime into a day or a month for use in GROUP BY (etc).