IN A TABLE HAVE ONE COLUMN PRIMARY KEY..IT WILL NOT ALLOWS NULL VALUES AND DUPLICATE VALUES..INSTEAD OF PRIMARY KEY WHY CANT WE USE UNIQUE AND NOT NULL.THESE TWO ALSO DOESNT ACCEPT NULL VALUES IN NOT NULL AND UNIQUE DOESNT ACCEPT DUPLICATE VALUES? SO WHAT IS THE DIFEERENCE BETWEEN(UNIQUE,NOT NULL) AND PRIMARY KEY??????

8 Answers   rsystems,

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