Question

I have simple query which is taking around 7-8 seconds for to retreive the data from database which I want to fine tune further to 2-3 seconds.

Table :

UpdateDateTime | field1 | field2 |..... FieldN.

Query is :

Select *  
from Table with (nolock)  
where UpdateDateTime Between D1 and D2  
Order By UpdateDateTIme  

I have created Clustered Index On UpdateDateTime

What could be done further to increase its Efficiency?

Answer 1

Reduce the number of columns returned is the obvious answer, then create a covering (nonclustered) index on UpdateDateTIme and INCLUDE the other selected columns.

CREATE NONCLUSTERED INDEX NC_MyCoveringIndex 
   ON Table(UpdateDateTime)
      INCLUDE (Col1, Col2, ..., ColN)

Ref.

[Note: It’s not ideal to create a wide covering index that includes all the columns in the table.]

A lot depends on how selective your WHERE clause is. If it returns (approximately) greater than 10% of the number of rows in the table, then the optimiser will probably just scan the clustered index anyway.

That’s pretty much it. Beyond you need to take a look at your hardware, and how much data you are pulling across the wire.