Select count(*)

 

Today I was reading(I always read Paul Randal).

http://www.sqlskills.com/BLOGS/PAUL/post/Which-index-will-SQL-Server-use-to-count-all-rows.aspx

I learned that whenever you query select count(*) it will select the the best plan… as

if no index —no option –table scan

INDEX: choose the smallest possible index(if has multiple index) to achieve the lowest I/O cost.

you can also test this with

set statistics io on

Thanx.

Vinay

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