What Is A Unique Key And Primary Key And Foreign Key?

1.	What Is A Unique Key And Primary Key And Foreign Key?
Answer» A UNIQUE KEY constraint is USED to ensure that there are no duplication VALUES in the field/column. A PRIMARY KEY constraint uniquely identifies each record in a database table. All columns PARTICIPATING in a primary key constraint must not contain NULL values. A FOREIGN KEY is a key used to LINK two tables together. A FOREIGN KEY in a table is linked with the PRIMARY KEY of another table.

Answer»

A UNIQUE KEY constraint is USED to ensure that there are no duplication VALUES in the field/column.
A PRIMARY KEY constraint uniquely identifies each record in a database table. All columns PARTICIPATING in a primary key constraint must not contain NULL values.
A FOREIGN KEY is a key used to LINK two tables together. A FOREIGN KEY in a table is linked with the PRIMARY KEY of another table.

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