title: Query times out when executed from web, but super-fast when executed from SSMS
body: <p>I'm trying to debug the source of a SQL timeout in a web application that I maintain.  I have the source code of the C# code behind, so I know exactly what code is running.  I have debugged the application right down to the line that executes the SQL code that times out, and I watch the query running in SQL profiler.   </p>
  
  <p>When this query executes from the web, it times out after 30 seconds.  However, when I cut/paste the query exactly as presented in Profiler, and I put it into SSMS and run it, it returns almost instantly.  I have traced the problem to ARITHABORT being set to OFF in the connection that the web is using (that is, if I turn ARITHABORT OFF in the SSMS session, it runs for a long time, and if I turn it back ON then it runs very quickly).  However, reading the description of ARITHABORT, it doesn't seem to apply...   I'm only doing a simple SELECT, and there is NO arithmetic being performed at all..   just a single INNER JOIN with a WHERE condition:</p>
  
  <p>Why would ARITHABORT OFF be causing this behavior in this context??  Is there any way I can alter the ARITHABORT setting for that connection from SSMS?  I'm using SQL Server 2008.</p>