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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:
Explain natural join? Natural Join - Similar as equi-join except in which the join attributes (having similar names) are not involved in the resulting relation. Only one sets
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Need a sample of a clinic database relationships
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An ideal data dictionary should have everything a DBA wants to know about the database. 1 Conceptual, External, and internal database descriptions. 2. Descriptions of attr
Shared lock or Read Lock It is requested by a transaction that needs to just read the value of data item. A shared lock on a data item does not permit an exclusive lock
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