Hi Simon,
I just stumbled about this post. > On 21.03.2011, at 06:34, Simon Slavin wrote: > > Suppose you have a TABLE employees with ten thousand rows and no indexes, and > you execute > > SELECT id,firstname,surname FROM employees WHERE firstname='Guilherme' AND > age=46 > > The query optimizer has a choice. It can first pick out all the Guilhermes, > and then find those who are the right age, or it can first pick out all the > 46 year olds, then find any with the right firstname. It has to do two > operations, and it must do the first one on the entire list of members. The > only way to make things faster is if the second operation needs to worry > about the smallest number of rows possible. There are only two options: name > first then age, or age first then name. > Is it really that way? I somehow assumed in that non-index case there is just a single table scan involved? Fetching each record, calculating firstname='Guilherme' AND age=46 for each, and selecting the matching records? confused, /eno _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
