indexing - Why is my Sql Server query plan using scans instead of seeks when joining data? -


comming mysql background i'm having difficulties understand what's wrong following setup.

i have 2 tables variable , dimension

both have primary key, variable furthermore has foreign key dimension named dimension_instance_1_uid, on index created.

when execute query 

select this_.name, dimensioni4_.name dbo.variable this_ inner join dbo.dimension_instance dimensioni4_ -- index hint nothing changes... -- (index(pk_dimension_instance)) on this_.dimension_instance_1_uid = dimensioni4_.uid

it seems if index isn't used seek , scan executed according execution plan. shows 2 index scan's instead of 1 index scan , 1 index seek.

enter image description here

i expect index seek because in case in dimension_instance 10 of 15k records match entries in variable table.

can shed light in misunderstanding of how ms sql indexes work.

the query execution plan , query optimizer estimate better operation regarding data inside db , other variables: in case maybe thinks query less costly doing index scan instead of seek: may caused low row numbers


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