Sorting small list (10 items) in PHP vs. MySQL and then returning?

Question

I'm curious what the runtime cost of sorting a small set of elements returned by a MySQL query is in PHP in contrast to sorting them in MySQL.

Reason I can't sort them in MySQL is because of the groups of data being returned, (actually 2 queries and then bringing data together PHP side).

Thanks!

NikiC · Accepted Answer · 2011-09-22 19:38:34Z

3

There will be no difference for ten elements. But generally you should always sort in MySQL, not PHP. MySQL is optimized to make sorting fast and has the appropriate data structures and information.

PS: Depending on the nature of the data you want to combine: Look at JOINs, UNIONs and subqueries. They'll probably do it.

answered Sep 22, 2011 at 19:38

NikiC

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2 Comments

DJSunny Over a year ago

Yeah I didnt think it would matter for so few elements. The bigger question I guess is "whats the cost of UNION in MYSQL", I tend to shy away from them and subqueries in the name of performance.

Marc B Over a year ago

@csjohn: fairly minimal. the cost of the two individual queries and (default) eliminating dupes, so no more expensive than 2 queries + select distinct on the whole results.

dkretz · Accepted Answer · 2011-09-22 19:49:25Z

2

My opinion:

The overhead is negligible in either case. Optimize your productivity and do whichever is easier for you. The computer is there to help you, not vice versa.

If you really want to optimize the host, have you considered letting the client do it in javascript?

I'd probably do it in SQL too, but mainly to keep the logic in one place (increase cohesion, reduce coupling).

edited Sep 22, 2011 at 19:49

answered Sep 22, 2011 at 19:43

dkretz

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1 Comment

DJSunny Over a year ago

I like the cut of your jib. I can't do that in this particular case, but I do indeed like to offload work to the clients.

user557846 · Accepted Answer · 2011-09-22 19:39:41Z

1

you could combine the queries with a union and then sort it with mysql

Q1
UNION
Q2
ORDER BY X

answered Sep 22, 2011 at 19:39

user557846

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