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Define entity integrity and referential integrity. How does SQL allow specification of these?
Ans: Entity Integrity Rule- If the attribute A of relation R is a prime attribute of R after that A cannot accept null values.
Referential Integrity Rule- In referential integrity, it is made sure that a value that appears in one relation for a given set of attributes as well appears for a particular set of attributes in another relation.
In SQL, referential integrity and entity integrity rules are implemented as constraints on the relation known as reference Key constraint and primary Key constraint correspondingly.
These constraints can be fixed with relation at the time of creation of the relations or after the creation of the relations by altering the definition of the relations. For instance:
What is meant by software and hardware RAID systems? RAID can be executed with no change at the hardware level, using only software modification. Such RAID implementations are
i have assignments I don''t have time to finish because of work and other assignments, can you help with this? All are from the book Darabase design, application development and a
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A super key is an attribute or set of attributes used to recognize the records uniquely in a relation. For instance, in the Relation PERSON defines earlier PERSON_ID is a super
What is NULL? Give an example to described testing for NULL in SQL? The NULL SQL keyword is used to represent either a missing value or a value which is not applicable in a re
The Third Normal Form (3NF) Even though, transforming a relation that is not in 2NF into a number of relations that are in 2NF take out many of the anomalies, it does not neces
What is Asterisk in SQL? Asterisk (*): In SQL, the columns for all the tables and views in the FROM clause will be displayed.
Explain the structure of well formed formulae in relational calculus. Ans: a. An atom is a formula b. If P1 is a formula, after that so are ¬P1 and (P1) c. If P1 and P2 a
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Control as a State Machine Engine First let us define the state machine: "the state machine is a machine which is an object but not an application object. It is a part of lang
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