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What's the difference between (NOT NULL + UNIQUIE) and Primary key.?
Is it provided for saving time and space? I means just for ease?
1 Resposta
+ 10
ā In unique constraint U can have null values , but in primary key constraint U can't have null values .
ā Duplicate values is not allowed in both .
ā U can say Primary key cons. = Unique & not-null together .