Re: does a table always need a PK?

Paul <paul_at_not.a.chance.ie> wrote in
news:MPG.19b1b482826a20ab989723_at_news1.eircom.net:

> Now, as I understand it, RDBMS's will look at the size of a table
> before scanning it to see if it's worthwhile using an index, and if
> the table is too small, it'll just perform a straigh scan anyway and
> not bother with the index, even if you've gone to the trouble of
> putting one in.

Aside what Venkat points out, the more complex the query (more tables in the join) it's possible that the above becomes grossly inefficient. In-memory table scans can be very costly when paired with (millions of) nested iterations.

-- 
Pablo Sanchez, Blueoak Database Engineering
http://www.blueoakdb.com