What is the difference between UNIQUE CONSTRAINT and
PRIMARY KEY?
1. There is no difference.
2. A PRIMARY KEY cannot be declared on multiple columns.
3. A UNIQUE CONSTRAINT cannot be declared on multiple
columns.
4. A table can have multiple PRIMARY KEYS but only one
UNIQUE CONSTRAINT.
5. A table can have multiple UNIQUE CONSTRAINTs but only
one PRIMARY KEY.
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Answer Posted / vikneswaran
1) primary key don't allow null values but unique const
allow null values
2)we can declare primary key as multiple column. but table
should have one primary key
3)we can declare unique as multiple column. but table should
have one unique key
4) and 5)
in table we can create multiple column of primary key and
multiple column of unique. but only the restriction is in
table should have one primary key and one unique key .. if
it is neccessary.
| Is This Answer Correct ? | 1 Yes | 2 No |
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