Why does putting a WHERE clause outside view have terrible performance

Question

Let\'s say you have a view:

CREATE VIEW dbo.v_SomeJoinedTables AS
SELECT
    a.date,
    a.Col1,
    b.Col2,
    DENSE_RANK() 
      OVER(PARTITION BY a.date, a.         


        

Answer 1

It's called "Predicate pushing" aka deferred filtering.

SQL Server doesn't always realise the WHERE can be applied "earlier", inside the view effectively.

It has been mitigated in SQL Server 2008 to work more as expected