http://sqlblog.com/blogs/alexander_kuznetsov/archive/2009/07/16/when-you-add-an-index-and-your-query-blows-up.aspxYou cannot assume that the conditions in your WHERE clause will evaluate in the left-to-write order - making such assumptions leads to unsafe queries. For example, the following query is not safe: SELECT * FROM dbo.Messages WHERE ISDATE ( VarcharColumnenCommunityServer 2.1 SP2 (Build: 61129.1)http://sqlblog.com/blogs/alexander_kuznetsov/archive/2009/07/16/when-you-add-an-index-and-your-query-blows-up.aspx#15459Fri, 24 Jul 2009 07:26:52 GMT21093a07-8b3d-42db-8cbf-3350fcbf5496:15459Marius<p>Hi Alexander,</p> <p>I got the same results as your.</p> <p>I am running:</p> <p>Microsoft SQL Server 2008 (RTM) - 10.0.1600.22 (Intel X86) &nbsp; Jul &nbsp;9 2008 14:43:34 &nbsp; Copyright (c) 1988-2008 Microsoft Corporation &nbsp;Express Edition with Advanced Services on Windows NT 5.1 &lt;X86&gt; (Build 2600: Service Pack 3) </p> http://sqlblog.com/blogs/alexander_kuznetsov/archive/2009/07/16/when-you-add-an-index-and-your-query-blows-up.aspx#17485Fri, 09 Oct 2009 21:23:49 GMT21093a07-8b3d-42db-8cbf-3350fcbf5496:17485Alexander Kuznetsov<p>Sounds trivial? Right, but different flavors of this myth still persist. Yesterday I noticed a thread</p> http://sqlblog.com/blogs/alexander_kuznetsov/archive/2009/07/16/when-you-add-an-index-and-your-query-blows-up.aspx#18097Wed, 21 Oct 2009 18:53:47 GMT21093a07-8b3d-42db-8cbf-3350fcbf5496:18097Dan<p>Thanks so much for the CASE trick to force data validation before sending the data to the CAST/CONVERT function. &nbsp;</p> <p>I found many places online that explained the issue at hand was that there was no guaranteed order to the WHERE execution, but you were the only one to provide a beautiful/simple/elegant solution.</p>