Answer / venkat rao

Unique key takes null value but primary key doesnot take
null value
primary key have properties of both null key and unique key
constraints

Answer / sudhanshu_kmr

.....primary key.......... unique key

at most one column .....:... any number of column

only unique values........... only unique values

don't accept null........... accept null

Answer / ashish asthana

Primay key restrict the duplicacy in the records and does
not accept null value or there are only one primary key in
a table

Unique constraint also restict the duplicacy but it accept
the null value one or more then one. We can apply unique
constraint more than one column

Answer / durai

primary key is does not allow duplicate which is contain not
null it is only once we can use in table

unique key allow null value

Answer / pradeep rajpoot

primary key no null value allow.
but unique key one null value is allow

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