[RESOLVED] Extra Fields vs Extra Queries

[Shawazi]

So I've been optimizing my site lately, if you haven't noticed all my efficiency questions. Here is the latest one:

Should I use a join in which I will definitely have 2 out of 4 fields that will never be used. PHP code would use these results to decide which fields to use.

OR

Should I only select the minimum fields and then have another query select the two fields I'm going to need. This would be decided using PHP based on results from the first query.

[Piranha]

It is really impossible to say without knowing how you use it and how your queries look like. My suggestion would be to try both out and use microtime to decide what is faster.

[Shawazi]

Never used that one before but just looked at the manual and I'm sure that will solve the question. Thanks.

[Shawazi]

In situation one, I selected 5 fields. I then used 4 of these fields to determine what table to get data from next using PHP.

In situation two, I selected 7 fields. I then used 4 of these fields to determine which of the extra two fields were needed. Since I did not need to make a second query ever, this was faster.

So it would seem, on this smaller scale, that less PHP lines/queries is better than returning MySQL results.

0.00248 seconds
vs
0.001394 seconds

Note: The queries are a lot more complex than listed here with joins and unions so the time is longer than a normal query either way.

Time was measured from before the first query to the end of some printed lines showing the data was selected properly.