Primary Key, Foreign key, Candidate key, Super key

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In this topic, you will learn about, Primary Key, Foreign key, Candidate key, Super key.

Primary key: A primary key, also called a primary keyword, is a key in a relational database that is unique for each record. It is a unique identifier, such as a driver’s license number, telephone number (including area code), or vehicle identification number (VIN). A relational database must always have one and only one primary key.

Foreign key: In the context of relational databases, a foreign key is a field (or collection of fields) in one table that uniquely identifies a row of another table. In simpler words, the foreign key is defined in a second table, but it refers to the primary key in the first table.

Candidate key: A Candidate Key can be any column or a combination of columns that can qualify as a unique key in a database. There can be multiple Candidate Keys in one table. Each Candidate Key can qualify as a Primary Key. Primary Key – A Primary Key is a column or a combination of columns that uniquely identify a record.

Super key: Super key is created the same as the primary key and automatically specify as super key with the help of relational function. The super key can represent a foreign key element in another relational table. Super key helps to inherit relational table records.

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