Comments on: Quick Tip: MySQL date_add

By: Tom

Tom — Sat, 05 Jun 2010 22:46:51 +0000

Or you can use this: DATE_SUB(NOW(), INTERVAL 1 DAY)

By: Metric Stormtrooper

Metric Stormtrooper — Tue, 25 May 2010 23:12:56 +0000

@Metric Stormtrooper: SELECT * FROM logs WHERE logstamp = ‘::php today() ::’

hm, cant post php syntax here, but you get the idea

By: Metric Stormtrooper

Metric Stormtrooper — Tue, 25 May 2010 23:10:14 +0000

@Niklas Berglund: your query must be deterministic – query might provide same result no matter how many times it is run, if data remains the same. So if your query uses non-deterministic functions such as NOW(), UUID(), RAND(), CONNECTION_ID() etc it will not be cached.
However, if you pass in a fixed value from PHP as in

SELECT * FROM logs WHERE logstamp = ”

it will be cached.

(the php function today() is just a one-liner that returns the current day in mysql format)

By: DeMx

DeMx — Fri, 21 May 2010 20:42:28 +0000

This query will not be used index.

By: Niklas Berglund

Niklas Berglund — Fri, 21 May 2010 16:15:44 +0000

@Jeremy Parrish: Why didnt I think of this? :) Thanks!

By: Jeremy Parrish

Jeremy Parrish — Fri, 21 May 2010 15:56:21 +0000

If you want caching to work, you can truncate the time part like this:

$yesterday = strtotime(‘-1 day’);
$yesterday_str = date(‘Y-m-d 00:00:00′, $yesterday);

Then it’ll be good for the whole day. This has the added benefit of matching the logical meaning of “yesterday” rather than being precicely 24 hours ago.

By: Niklas Berglund

Niklas Berglund — Fri, 21 May 2010 15:28:07 +0000

Hmm good tip indeed, but… The queries still cannot be cached if you use something as dynamic as strtotime(‘now’), isn’t that right?

So using strtotime() does not enable the query to be cached? Or am I wrong?
strtotime() would only give you an advantage if the same query is run during the same second?

By: David Walsh

David Walsh — Fri, 21 May 2010 15:17:47 +0000

@macol: Ohhhh, good tip!

By: macol

macol — Fri, 21 May 2010 14:38:06 +0000

I prefer using php function strtotime() because queries using MySQL functions like NOW() can’t be cached

By: Niklas

Niklas — Fri, 21 May 2010 13:50:30 +0000

Or you can do it like this: date_starts >= NOW() – INTERVAL 1 DAY
Easier to read in my opinion :) Good tip! I do it like this quite often