What's a key in database?

What is a key in SQL?

An SQL key is either a single column (or attribute) or a group of columns that can uniquely identify rows (or tuples) in a table. SQL keys ensure that there are no rows with duplicate information. Not only that, but they also help in establishing a relationship between multiple tables in the database.

What is the purpose of key?

A key is a specially shaped piece of metal that you place in a lock and turn in order to open or lock a door, or to start or stop the engine of a vehicle. She reached for her coat and car keys. The keys on a computer keyboard or typewriter are the buttons that you press in order to operate it.

What is key and primary key?

Primary Key is a column that is used to uniquely identify each tuple of the table. ... Difference between Primary Key and Unique Key.Primary KeyUnique KeyOnly one primary key can be present in a tableMultiple Unique Keys can be present in a table

How do database keys work?

Keys are very important part of Relational database model. They are used to establish and identify relationships between tables and also to uniquely identify any record or row of data inside a table. A Key can be a single attribute or a group of attributes, where the combination may act as a key.