How much SQL Query is too much SQL Query?

Question

I was researching for a CMS to use and ran into a review on vBulletin 4.0; using about 200 queries on one page load.

I was then worried.

Further research brought me to other sites to see how much queries they are using and I found that some forum software such as Invision Power Board and PHPBB are using queries as low as 6 or 8.

Currently, my site uses about 25 to 40 queries.

Should I be worried?

Answer 1

Don't be worried about number of queries.

Be worried about:

1. Pages loading too slowly
2. The SQL being too complicated to maintain.

Clarification:

SQL being too complicated can come from either too many queries OR a few queries that are very complicated (lots of joins and sub queries, etc).

Answer 2

If you aim for something, aim for 3 reads and 1 writes per HTTP hit.

While these are arbitrary numbers (somehow, they are actually taken from the Advanced PHP Programming), they emphasize the ideas:

• the number of SQL roundtrips should be low, under 10 for sure, per HTTP call
• there is a difference between reads and writes, and the ratio should favour reads. writes create contention

Also remember that not all reads are equal: the 3 reads should be highly optimized reads, not full table scans with 4-5 outer joins...