sql - What are the pros/cons of using a synonym vs. a view?

Question

This is a generic database design question - What are the benefits of using a synonym in database development, over a simple view? What are the main considerations to keep in mind when choosing between the two?

An example view:

CREATE VIEW Users AS
SELECT * FROM IdentitySystem.dbo.Users

And the equivalent synonym:

CREATE SYNONYM Users 
FOR IdentitySystem.dbo.LCTs

Answer 1

They are different things. A synonym is an alias for the object directly, a view is a construct over one or more tables.

Some reasons to use a view:

• May need to filter, join or otherwise frig with the structure and semantics of the result set

• May need to provide legacy support for an underlying structure that has changed but has dependencies that you do not want to re-work.

• May provide security where some of the contents of the table should be visible to a class of users but not all. This could involve removing columns with sensitive information or filtering out a subset of the records.

• May wish to encapsulate some business logic in a form that is accessible to users for reporting purposes.

• You may wish to unify data from more than one source.

... Plus many more.

Reasons to use a synonym:

• You may wish to alias an object in another database, where you can't (or don't want to) hard code the reference to the specific database.

• You may wish to redirect to a source that changes over time, such as an archive table.

• You want to alias something in a way that does not affect the query optimiser.

... Plus many more.