Sql COUNT Performance Question

Question

Structure of Example table:

Id, Integer (PK)
Name, Varchar(100)
Description, Text

I need to know if exists difference in performance between:

SELECT COUNT(*) FROM Example;

and

SELECT COUNT(Id) FROM Example;

Or does not exists differences?

Answer 1

Differences exist in both performance and the actual resultset

Performance of COUNT SQL function

Answer 2

Check the explain plan: does the result come from the table or from meta data (e.g. INFORMATION_SCHEMA)?: The differences are likely to be very minimal.

Answer 3

I would believe that there is a difference; depending on the size of your table, it could be negligible, or it could be significant.

This is probably the slowest: SELECT COUNT(*) FROM Example
This is in the middle: SELECT COUNT(Id) FROM Example
This would be fastest: SELECT COUNT(1) FROM Example

Answer 4

Worth reading, but unfortunately in russian.

COUNT(*), could it be faster?

Short story is that COUNT(*) is not so efficient as direct access to the dm_db_partition_stats.