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Why mentioning NOT NULL while applying PRIMARY KEY constraint?
According to my experience with databases you don't need to do so!
2 odpowiedzi
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Just an extra precaution to make sure it always has a value. Can really mess things up otherwise.
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I know what's the meaning of PK, my input was about that PK = NOT NULL + UNIQUE + INDEX
why they need to mention NOT NULL twice at the table creation?