SQL Server Clustered index scan vs Clustered index seek

Dear Friends,

Yesterday and day before we have covered Clustered Index Seek and Clustered index Scan. In today’s post, let us draw a comparison between SQL Server clustered index scan vs clustered index seek.

Let us first reproduce CI Scan by running SELECT statement on Person.Address table.

USE [AdventureWorks2012]

SELECT * FROM Person.Address

And now turn on STATISTICS IO and STATISTICS TIME one by one then run same query.

USE [AdventureWorks2012]

SET STATISTICS IO ON

SELECT * FROM Person.Address

USE [AdventureWorks2012]

SET STATISTICS TIME ON

SELECT * FROM Person.Address

We will now run the same query that we used yesterday to get CI seek operator first for illustration.

USE [AdventureWorks2012]

SELECT Address.AddressID,Address.AddressLine1,Address.City,Address.PostalCode
FROM Person.Address
WHERE Address.AddressID = 14918

Time to turn on STATISTICS IO and STATISTICS TIME one by one followed by running same query.

USE [AdventureWorks2012]

SET STATISTICS IO ON

SELECT Address.AddressID,Address.AddressLine1,Address.City,Address.PostalCode
FROM Person.Address
WHERE Address.AddressID = 14918

USE [AdventureWorks2012]

SET STATISTICS TIME ON

SELECT Address.AddressID,Address.AddressLine1,Address.City,Address.PostalCode
FROM Person.Address
WHERE Address.AddressID = 14918

By looking at the output(s), we can very well understand both logical reads as well as elapsed time is reduced for CI seek operation and is better of the two operators in question.

Note: This is just an illustration and results may vary under different circumstances as per environment.

Happy learning!

Regards,

Kanchan

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