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WHAT IS DIFFERENCE BETWEEN UNIQUE+NOT NULL AND PRIMARY KEY?

April 26, 2017difference key null primary

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WHAT IS DIFFERENCE BETWEEN UNIQUE+NOT NULL AND PRIMARY KEY?

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Ans: Unique and Not Null is a combination of two Constraints that can be present any number of times in a table and can’t be a referential key to any column of an another table where as Primary Key is single Constraint that can be only once for table and can be a referential key to a column of another table becoming a referential integrity.