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Explain the concept of a data model ?
Data Model - Model is an abstraction procedure which hides irrelevant details although highlighting details relevant to the applications at hand. As same, a data model is a collection of concepts which can be used to elaborate structure of a database and gives the essential means to achieve this abstraction. Structure of database means the data types, relationships, and constraints which should hold for the data. In common a data model consists of two elements:
• A mathematical notation for expressing relationships and data.• Operations on the data which serve to express queries and other manipulations of the data.
Wait-die" scheme : The idea is based on non-preventive method. It is based on a simple rule: If Ti requests a database resource that is held by T
Prepare Heart Failure Registry database How are you today? Please I would like you to design a Heart Failure registry where doctors will log in to enter information about their
explain concept of decomposition?
The Concurrent Transactions Almost every commercial DBMS support multi-user environment. Therefore, allowing multiple transactions to proceed concurrently. The DBMS must make
What are two special events? The two special events are as "entry" and "exit". Any action which is marked as linked to entry event is executed whenever given state is entered v
Increased overheads on update : On the drawbacks side, it will need the system to ensure that all replicas of a relation are consistent. This shows that all the replicas of the rel
What is Alternate Key Alternate Key: This is the candidate key which is not taken as the primary key of the table. They are named so because although not the primary key, the
What are the several forms of identity? a) Value b) Name c) Built-in
Q. Define a weak entity set and its identifying relationship. List the necessary conditions for a meaningful identifying relationship set of a weak entity set. Entity is a t
Relations create the database. They must satisfy various properties, like no duplicate tuples, no ordering of tuples, and atomic attributes, etc. Relations that satisfy these basic
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