what is primary key,unique key, foreign key? can u teach me
in simple language?
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Answer Posted / doraswamy
One table allows only one primary key but there is no
restriction for unique keys.
These two are same but one difference is unique key will
allow nulls.
Primary key create on a combination of mulitiple colums.
Foreign key is reference of another table primiary key. It
will not allow null values.
~Doraswamy
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