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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:
Describe the objective of Structural Diagrams The main objective of structural diagram is to visualize, construct, specify and document static aspects of a system. Their eleme
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Write short notes on domain relational calculus The domain relational calculus uses domain variables that take on values from an attribute domain rather than values for whole
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Define NULL value NULL value NULL means something is unknown. It does NOT mean null (the digit 0). Null is as well employed as attribute value for a particular entity in which
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Consider the relations: PROJECT(proj#,proj_name,chief_architect) EMPLOYEE(emp#,emp_name) ASSIGNED(proj#,emp#) Use relational algebra to express the subsequent queries: (i) Get
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