viewquestions/12437/ Define referential integrity constraint Explain the importance of referential integrity constraint Database Management Systems 10CS54 VTU notes 8 Marks Jun July 2013 5 Marks Dec 14Jan 15

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How does SQL inplement the entity integrity constraints of relational Data Model? Database Management Systems - 10CS54 VTU notes 4 Marks (Dec/Jan 2014, Jun / July2013)(8 marks Dec 14/Jan 15)

 Explain with an example?


By:anonymousguy7799

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In general, an update on a view on defined on a single table w/o any aggregate functions can be mapped to an update on the base table More on Views 
We can make the following observations: 
• A view with a single defining table is updatable if we view contain PK or CK of the base table 
• View on multiple tables using joins are not updatable • View defined using grouping/aggregate are not updatable VTUlive.com 30 • Specifying General Constraints 
• Users can specify certain constraints such as semantics constraints 
CREATE ASSERTION SALARY_CONSTRAINT CHECK ( NOT EXISTS ( SELECT * FROM EMPLOYEE E, EMPLOYEE M, DEPARTMENT D WHERE E.SALARY > M. SALARY AND E.DNO=D.NUMBER AND D.MGRSSN=M.SSN)) 

Nikhil-bharadwaj

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