Answer / janhvee

diff. between primary key and unique is unique key can be
null but primary key can't be null.

one table can have only one primary key but unique key can
be multiple keys

Answer / rakesh ranjan

IN PRIMARY KEY IS ONLY IN ANY TABLE BUT WHEN WE TALKING
ABOUT UNIQUE KEY, IT CAN BE NULL.

Answer / jeyaprakash

primary is not allow null value.but unique can be allow null
value

Answer / sonu kumar

primary of any table can't be null but unique can be
primary key may be a unique key but unique can't be a primary key b/c primary key of any relation cant be a null value

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