A derived table is one that is created on-the-fly using the SELECT statement, and referenced just like a regular table or view. Derived tables exist in memory and can only be referenced by the outer SELECT in which they are created. A simple use of a derived table is shown here.

The inner SELECT produces a derived table and replaces a regular table or view. The key thing to remember when using derived tables is that you must always use an alias (e.g., AS a). The following shows the error produced when the alias is omitted.

which is better view or derived tables?
i feel there is no difference.

When a view is referenced the SELECT of the view is
merged into the SELECT that refereces it, so it is really the same
thing.  Of course views save a lot of coding, once written are less
subject to errors, and can have permissions assigned.

but,

when considering logical data independence, security and 
 reusability as important aspects, using views may be preferred over writing 
 derived tables over and over again. 
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