Comments on: The effects of DISTINCT in a SQL query http://webbtechsolutions.com/2009/07/24/the-effects-of-distinct-in-a-sql-query/ We provide clever, unique, and flexible solutions Sat, 21 Jan 2012 18:33:58 +0000 hourly 1 http://wordpress.com/ By: My Most Popular Posts From 2010 « WebbTech Solutions http://webbtechsolutions.com/2009/07/24/the-effects-of-distinct-in-a-sql-query/#comment-953 Thu, 27 Jan 2011 12:05:40 +0000 http://webbtechsolutions.com/2009/07/24/the-effects-of-distinct-in-a-sql-query/#comment-953 [...] The effects of DISTINCT in a SQL query [...]

]]> By: Joe Webb http://webbtechsolutions.com/2009/07/24/the-effects-of-distinct-in-a-sql-query/#comment-163 Mon, 17 Aug 2009 11:05:50 +0000 http://webbtechsolutions.com/2009/07/24/the-effects-of-distinct-in-a-sql-query/#comment-163 Thanks Suman. I’m glad you’ve found these posts useful.

Joe

]]> By: Suman http://webbtechsolutions.com/2009/07/24/the-effects-of-distinct-in-a-sql-query/#comment-162 Mon, 17 Aug 2009 08:59:51 +0000 http://webbtechsolutions.com/2009/07/24/the-effects-of-distinct-in-a-sql-query/#comment-162 Thank you very much for the details of DISTINCT clause! It gave a clear picture

]]> By: The effects UNION in a SQL query | ButtonForums http://webbtechsolutions.com/2009/07/24/the-effects-of-distinct-in-a-sql-query/#comment-153 Wed, 12 Aug 2009 07:04:59 +0000 http://webbtechsolutions.com/2009/07/24/the-effects-of-distinct-in-a-sql-query/#comment-153 [...] In a recent blog, I shared some of the natural but sometimes unanticipated consequences of adding DISTINCT to a SELECT statement. Adding DISTINCT ensures that you don’t have duplicated rows in your result set, but that assurance comes at a price. Performance is typically impacted negatively when you add DISTINCT to a query. You can read the blog and see the proof here. [...]

]]> By: The effects UNION in a SQL query « WebbTech Solutions http://webbtechsolutions.com/2009/07/24/the-effects-of-distinct-in-a-sql-query/#comment-140 Thu, 06 Aug 2009 13:32:42 +0000 http://webbtechsolutions.com/2009/07/24/the-effects-of-distinct-in-a-sql-query/#comment-140 [...] The effects UNION in a SQL query In a recent blog, I shared some of the natural but sometimes unanticipated consequences of adding DISTINCT to a SELECT statement. Adding DISTINCT ensures that you don’t have duplicated rows in your result set, but that assurance comes at a price. Performance is typically impacted negatively when you add DISTINCT to a query. You can read the blog and see the proof here. [...]

]]> By: wardany http://webbtechsolutions.com/2009/07/24/the-effects-of-distinct-in-a-sql-query/#comment-139 Wed, 05 Aug 2009 02:48:04 +0000 http://webbtechsolutions.com/2009/07/24/the-effects-of-distinct-in-a-sql-query/#comment-139 thanks….this is very usefull

]]> By: AjarnMark http://webbtechsolutions.com/2009/07/24/the-effects-of-distinct-in-a-sql-query/#comment-138 Mon, 03 Aug 2009 19:22:25 +0000 http://webbtechsolutions.com/2009/07/24/the-effects-of-distinct-in-a-sql-query/#comment-138 Hi Joe! At the end you ask for experiences or alternatives. One alternative that I have found, is putting additional criteria in the join clause, which I wrote about here: http://www.sqlteam.com/article/additional-criteria-in-the-join-clause.

I recently ran into this again, when debugging a query that joined to a junction table and needed additional criteria in order to return only one row instead of multiple (e.g. LEFT JOIN myJunction as J ON T1.Key1 = J.Key1 AND J.Key2 = ‘KnownLimitingValue’).

A few months ago I also wrote on this subject, not so much from a performance point of view, but from an accuracy point of view. See http://weblogs.sqlteam.com/markc/archive/2008/11/11/60752.aspx.

]]> By: Andre Araujo http://webbtechsolutions.com/2009/07/24/the-effects-of-distinct-in-a-sql-query/#comment-136 Sun, 02 Aug 2009 23:12:16 +0000 http://webbtechsolutions.com/2009/07/24/the-effects-of-distinct-in-a-sql-query/#comment-136 Nice post! Having spent a lot time tuning SQL queries, I’ve learned to be suspicious of any queries that use DISTINCT. Some times the use is legitimate, but more frequently you can get rid of them with properly SQL manipulation.

]]> By: Log Buffer #156: a Carnival of the Vanities for DBAs | Pythian Group Blog http://webbtechsolutions.com/2009/07/24/the-effects-of-distinct-in-a-sql-query/#comment-129 Fri, 31 Jul 2009 22:33:38 +0000 http://webbtechsolutions.com/2009/07/24/the-effects-of-distinct-in-a-sql-query/#comment-129 [...] Webb of WebbTech exposes the effects of DISTINCT in a SQL query, introducing it thus: “Many people (not those mentioned previously) resort to using the [...]

]]> By: Something for the weekend 31/07/09 | John Sansom - SQL Server DBA in the UK http://webbtechsolutions.com/2009/07/24/the-effects-of-distinct-in-a-sql-query/#comment-128 Fri, 31 Jul 2009 16:28:04 +0000 http://webbtechsolutions.com/2009/07/24/the-effects-of-distinct-in-a-sql-query/#comment-128 [...] The effects of DISTINCT in a SQL query [...]

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