sql - position of conditional parameters does matter in execution time? -


I have a database table with more than 3.5 million lines, where I am active user ( bit Columns) where the name is in the AR first name column ( nvarchar (100) ).

I have not applied over firstname to an index .

I wrote a question like: 

  Select * From the table where isActive = 1 and firstname '% ar%' taken Time: ~ 17s

and the second one like this: 

  Select from the table where the first name '% ar%' and isActive = 1 took the time: ~ 2s

I do not get what's happening behind the curtain. Can you please tell me how does SQL Server 2008 R2 take it?

When implementing such situations, should I keep in mind the other things?


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