The two big advantages of computed columns are:

1) a consistent definition;

2) defined in only one place.

1) If you define a computed column in the table, you know that all queries are using the same computation to generate the new value. If you specify the computation itself in different queries and views, some of them could be different from each other, possibly even to the extent of making the value incorrect.

2) Say you need to change/update the computation. With a computed column, you simply drop the old definition and add the new one -- all queries automatically now refer to the new definition. If you've done the computation in multiple queries/views, you must find them all and change them -- NOT fun.

For example:

ALTER TABLE dbo.tablename ADD

full_name AS

first_name +

ISNULL(' ' + middle_name, '') +

last_name

--requirement comes in to add a possible "salutation" to full_name

ALTER TABLE dbo.tablename

DROP COLUMN full_name

ALTER TABLE dbo.tablename ADD

full_name AS

ISNULL(salutation + ' ', '') +

first_name +

ISNULL(' ' + middle_name, '') +

last_name

Voila: every use of full_name from then automatically includes the required "salutation" with no other coding changes required.