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For every n-ary relationship type R where n>2, we make a new table S to represent R. We contain as foreign key attributes in s the primary keys of the relations that show the participating entity types. We also contain any easy attributes of the n-ary relationship type (or easy components of complete attributes) as attributes of S. The primary key of S is generally a combination of all the foreign keys that reference the relations showing the participating entity types. Figure is a special case of n-ary relationship: a binary relation.
Differance between internal and external schema? Internal and external schema: Internal Schema • Describes the physical storage structure • Uses a physical data model External
What is known as a search key? An attribute or set of attributes used to look up records in a file is known as a search key.
Types of Data fragmentation
What is the use of Union and intersection operation? Union: The result of this operation contains all tuples that are either in r1 or in r2 or in both r1 and r2.Duplicate tuple
Define union compatibility? Explain why INTERSECTION of two relations cannot be performed if they are not union compatible? Two relations R(A1, A2,-------, An) and S(B1, B2,--
explain the level architectures of the database management system
Explain the Exec statement in SQL Ans: Exec statement has the structure EXEC SQL END-EXEC Embeded SQl statements are of a form identical to non embedded SQL statem
Describe the primary key functions? Primary Key : The primary key is an attribute or a set of attributes in which uniquely identify a specific example of an entity. Every entit
define locking in simple language and decribed it
What is Trigger? A trigger is a SQL procedure that initiates an action when an event (INSERT, DELETE or UPDATE) occurs. Triggers are kept in and managed by the DBMS. Triggers a
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