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Update Operations and Dealing with Constraint Violations
There are three basic operations to be executes on relations:
The INSERT Operation:
The insert operation permits us to insert a new tuple in a relation. When we try to insert a new record, then any of the following four types of constraints can be violated:
• Entity Integrity constraint: If the primary key attribute value of new tuple t is given as null.
To do the division operation R1 ÷ R2, R2 should be a correct subset of R1. In the following example R1 have attributes A and B and R2 have only attribute B so R2 is a correct subse
Define the terms 1) physical schema 2) logical schema. Physical schema: The physical schema explains the database design at the physical level, which is the lowest level of abs
What is the function of IO/M signal in the 8085? It is a status signal. It is used to differentiate among memory locations and I/O operations. When this signal is low (IO/M = 0
A constraint named less_than_20 was defined on the field date_of_birth of table student. Delete this constraint. ALTER TABLE student DROP CONSTRAINT less_than_20;
Define deadlock avoidance. An alternative method for avoiding deadlocks is to needs additional information about how resources are to be requested. Each request requires the s
List the Armstrong's axioms for functional dependencies. What do you understand by soundness and completeness of these axioms? Ans: The Armstrong's axioms are: F1:
Explain about database system structure? Storage manager Authorization and integrity manager Transaction manager File manager Buffer manager Storage manager
The First Normal Form (1NF) Let us first describe 1NF: Definition: A relation (table) is in 1NF if 1. There are no duplicate tuples or rows in the relation. 2.
Optimistic Concurrency Control Is locking the only way to stop concurrency related problems? There exist some other ways too. One such way is known as an Optimistic Concurrency
limitations and benefits in database tecknowlagy
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