The only difference once MySQL parses these two queries is the first one is a LEFT JOIN, which will produce all records from the blogs table even if there is no matching record in the users table. The second query produces an INNER JOIN which means only rows with matching records in both tables will be returned.
Which one is faster? Probably the second since NULLs do not have to be considered -- probably not much faster though. Which one is better? That'll depend on your needs, if you only need records from both tables that have a matching row in the other, the second is better. If you need all blogs, even those without a matching user (can that even occur?), the first one is better. I prefer to write the INNER JOIN out though because it leaves my WHERE clause to do filtering. JW On Mon, Apr 25, 2011 at 9:42 AM, Andre Polykanine <an...@oire.org> wrote: > Hello everyone, > Sorry for my beginner question. Actually I have been using MySql for a > long time but I just start using some advanced things (earlier I > accomplished those tasks with PHP), so I will be asking stupid > questions, please bear with me. > Here is the first one. > We have two queries: > SELECT `blogs`.* FROM `Blogs` LEFT JOIN `Users` ON > `Blogs`.`UserId`=`Users`.`Id`; > and the following one: > SELECT `Blogs`.* FROM `Blogs`, `Users` WHERE > `Blogs`.`UserId`=`Users`.`Id`; > > 1. Are they identical? > 2. Which is better (faster, more optimal, more kosher, I mean, better > style...)? > Thanks! > > > -- > With best regards from Ukraine, > Andre > Skype: Francophile > Twitter: http://twitter.com/m_elensule > Facebook: http://facebook.com/menelion > > > -- > MySQL General Mailing List > For list archives: http://lists.mysql.com/mysql > To unsubscribe: http://lists.mysql.com/mysql?unsub=joh...@pixelated.net > > -- ----------------------------- Johnny Withers 601.209.4985 joh...@pixelated.net
