Question

what is primary key and foreign key?​

Answer 1

Primary Key -
A primary key is a key in a relational database that is unique for each record.

Foreign Key-
In relational databases, a foreign key is a field in one table that
uniquely identifies a row of another table or the same table.

Hope that helps!

Answer 2

Answer:

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A primary key is either an existing table column or a column that is specifically generated by the database according to a defined sequence.

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• It should always store some values .No bull values are allowed in primary key fields.
• It should store unique value.
• Once decided, the value must not change as long as that record remains in the database .

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A foreign key is a column (or columns) that references a column (most often the primary key) of another table.