what is primary key and what is Unique key? and differences between them?
primary key & Unique key
(2 posts) (2 voices)-
Posted 1 year ago #
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primary key is nothing but unique key for a table with no Null value
Unique key also same as primary key but it may have Null values.
Differences between Primary key and Unique key
- primary key does not have Null values, but Unique key may have
i.e,
Primary Key = Unique + No Null values
Unique Key = Unique + it may have Null values - One table contains only one primary key, but it may contains more than one unique keys.
Posted 1 year ago # - primary key does not have Null values, but Unique key may have
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