Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people, just like you, are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
Solved

constant scan in execution plan

Posted on 2009-04-13
3
1,961 Views
Last Modified: 2012-05-06
I have found a constant scan in my execution plan. Can someone tell me under what condition a constant scan would happen.
0
Comment
Question by:david_32
3 Comments
 
LVL 12

Expert Comment

by:udaya kumar laligondla
ID: 24135890
it looks like you are using GETDATE() function in a insert statement or do you have a partitioned table.
read more at
http://scarydba.wordpress.com/2008/07/01/constant-scan-in-execution-plans/
0
 
LVL 57

Accepted Solution

by:
Raja Jegan R earned 500 total points
ID: 24136248
Its not that you will obtain a Constant Scan when you use a partitioned table.

From MSDN,

Constant Scan

The Constant Scan logical and physical operator introduces a constant row into a query. It will return either zero or one row, which usually contains no columns. A Compute Scalar operator is often used to add columns to the row produced by a Constant Scan.

When you add a new column to a row / Result set using a Scalar function, then you will have a Constant Scan.

Say you have a function named dbo.format and if you use it in your query like

SELECT col1, col2, dbo.format(col3)
FROM urtable

It will have a constant scan.

Whenever you have a scalar function in your query to return some value, For eg, GETDATE() as mentioned earlier, SUBSTRING, LEN, CONVERT, CAST
You will end up in a constant scan.
0
 

Author Closing Comment

by:david_32
ID: 31569796
thanks
0

Featured Post

Ransomware: The New Cyber Threat & How to Stop It

This infographic explains ransomware, type of malware that blocks access to your files or your systems and holds them hostage until a ransom is paid. It also examines the different types of ransomware and explains what you can do to thwart this sinister online threat.  

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Recently, when I was asked to create a new SQL 2005 cluster, Microsoft released a new service pack for MS SQL 2005 what is Service Pack 3. When I finished the installation of MS SQL 2005 I found myself troubled why the installation of SP3 failed …
Use this article to create a batch file to backup a Microsoft SQL Server database to a Windows folder.  The folder can be on the local hard drive or on a network share.  This batch file will query the SQL server to get the current date & time and wi…
Established in 1997, Technology Architects has become one of the most reputable technology solutions companies in the country. TA have been providing businesses with cost effective state-of-the-art solutions and unparalleled service that is designed…

840 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question