Why is SQL Server using index scan instead of index seek when WHERE clause contains parameterized values

Question

We have found that SQL Server is using an index scan instead of an index seek if the where clause contains parametrized values instead of string literal.

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Answer 1

Try

declare @val1 nvarchar(40), @val2 nvarchar(40);
set @val1 = 'val1';
set @val2 = 'val2';

select 
    min(id) 
from 
    scor_inv_binaries 
where 
    col1 in (@val1, @val2) 
group by 
    col1
OPTION (RECOMPILE)