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Describe queries with complex types?
The present extension of the SQL query language deal with the complex type
Let us start with the simple example:
Find the title and the name of the publisher of each book this query carries out the task:
Select title, publisher.name
From books
path expression
The reference are dereference in 1999 by the -> simple
Select head-> name, head->address
From dept
An expression such as" head->name" is called the path expression.
Collection valued attributes
Nesting and unnesting
The transformation of the nested relation in to a form with fewer (or no) the relation -valued attribute value is known as unnesting
The reverse process of transformation a INF relation into a nested relation is known as nesting.
Find the names of all Albums that have more than 30 tracks. Result: (name: varchar(255))
Assume that you are responsible for selecting a new DBMS product for Sohar Hospital
Define- relational algebra. The relational algebra is a procedural query language. It having of a set of operations that take one or two relation as input and make a new relati
Foreign Keys and NULL Let us take the relation: DEPT DEPT ID DNAME BUDGET D1 M
er diagtram for icici
What are domain constraints? A domain is a set of values that might be assigned to an attribute .all values that appear in a column of a relation must be taken from the similar
Software failures : In such cases, a software error abruptly stops the implementation of the current transaction (or all transactions), therefore leading to losing the state of pr
Determine the OBJECTIVES of object design After passing through this unit, you should be able to: describe and apply concept of generalisation; understand and appl
.#question. Discuss the problem which may arise during concurrency control and recovery in distributed database which are not encountered in controlized database environment.
The Internal or Physical Level The collection of files permanently stored on secondary storage devices is called as the physical database. The internal or physical level is t
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