Difference between primary key and unique key ?
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Answer Posted / deen dayal sharma
1. PRIMARY KEY & UNIQUE KEY both uniquely identity of each
row in a table.
2. BOTH keys will not contain repeated value.
3. One table may have more than one Unique Key Constraint But
it should have only one Primary Key Constraint column.
4. BUT UNIQUE KEY will contain NULL value but PRIMAY key will
not contain NULL value.
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