On Mon, Feb 9, 2009 at 9:41 AM, Steven Buehler <steve@stripped> wrote:
> Ok, I just saw a post about using view's in mysql. I tried to look it up
> and found how to use it, but my question is: what is a view and why would
> you use it? Is it like a temporary table? Does it write a new database to
> the disk or use memory?
A view is a piece of SQL whose result can be queried like a table. It
stores no data; the results are always generated as the query
executes. In some cases it does use a temporary table to hold the
result and then query against it; in other cases it merges the
original query's SQL and the view's SQL together and then executes the
resulting query.
Why use it? To abstract a complex bit of code away for simplicity.
To grant permissions in a certain way (you can grant access to the
view and deny access to the underlying table).
There's a lot of complexity to it though, in terms of how to use views
correctly and get good performance. I think the manual goes over it
in good detail, and our book High Performance MySQL 2nd Edition has
probably the best exploration of it otherwise.
Baron
--
Baron Schwartz, Director of Consulting, Percona Inc.
Our Blog: http://www.mysqlperformanceblog.com/
Our Services: http://www.percona.com/services.html
