Where we are going to use "Derived Tables" (In which scenario they are mandatory) ?

Posted on 2008-11-09
Medium Priority
Last Modified: 2012-05-05

Can you please let me know in which scenarios derived tables are mandatory to use ?

Question by:milani_lucie
LVL 143

Expert Comment

by:Guy Hengel [angelIII / a3]
ID: 22917376
from syntax point of view, they are not "mandatory". you could always solve the problem with temp tables.
from performance point of view, they are very useful and powerful.
LVL 17

Accepted Solution

HoggZilla earned 1500 total points
ID: 22917383
Agreed, I prefer the use of derived but not required.
LVL 22

Expert Comment

ID: 22917500
A "derived table" is a syntax for creating a temporary name (alias) for a table expression within the scope of a single query. It is used mainly to simplify the SQL by using the name instead of repeating a complex expression.

The only time I can think of when derived tables are essential is for recursive queries (recursive CTEs). A recursive CTE (Common Table Expression) is a special kind of derived table.

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