http://msdn.microsoft.com/en-us/library/ms189292.aspx#BKMK_persisted

'You can create an index on a computed column that is defined with a deterministic, but imprecise, expression if the column is marked PERSISTED'

--If I wanted to find all those who received a work permit on a give day, this query works but shows a table scan.

SELECT [DOWorkPermit] FROM [Employee_2] WHERE [DOWorkPermit] = '12/31/1993';

--Add an index on the persisted, computed column:

CREATE NONCLUSTERED INDEX IX_WorkPermit ON [Employee_2] ([DOWorkPermit]);

GO

--The query still shows a table scan because DOBirth is in the output list and is needed to find the computed DOWorkPermit day:

SELECT [DOWorkPermit] FROM [Employee_2] WHERE [DOWorkPermit] = '12/31/1993';

-- drop and recreate the index including the DOBirth column

DROP INDEX IX_WorkPermit ON [Employee_2];

GO

CREATE NONCLUSTERED INDEX IX_WorkPermit ON [Employee_2] ([DOWorkPermit]) INCLUDE ([DOBirth]);

GO

--an index scan is now used

SELECT [DOWorkPermit] FROM [Employee_2] WHERE [DOWorkPermit] = '12/31/1993'

My question is, couldn't an index seek be done on the persisted, indexed value rather than having to compute it while doing a scan? Is it because there's only 1 record in the table or am I missing or misinterpreting something...