Execution plan, SQL Server 2012

Question

I have a question about execution plan:

I wrote a query before I approve it execution plan use clustered index scan with 2 row on reads:

Table 'Worktable'. Scan count 1, logical reads 17
Table 'a21'. Scan count 3, logical reads 6

after I create index seek execution plain use index seek

Scan count 43, logical reads 86.

What's better?

Thanks

Answer 1

You can't tell from the numbers because it does not show you which reads were physical, which were logical and how costly each read was. The read/write numbers are almost worthless.

Instead, measure CPU time used. For your workload it is extremely likely that there is no physical IO because the tables are so small. So don't measure IO.

Also, compare the execution plans.