Derived tables are SELECT statements that act as tables in the FROM clause. In various scenarios these can provide better performance than temporary tables. Consider following piece of script where i have used derived table
USE AdventureWorks GO SELECT DISTINCT s.PurchaseOrderNumber FROM Sales.SalesOrderHeader s INNER JOIN ( SELECT SalesOrderID FROM Sales.SalesOrderDetail ) d ON s.SalesOrderID = d.SalesOrderID
commands following the JOIN statement are working as derived table.