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keys in DBMS

Last Updated: November 19, 2018 by Chaitanya Singh | Filed Under: DBMS

Key plays an important role in relational database; it is used for identifying unique rows from table. It also establishes relationship among tables.

Types of keys in DBMS

Note: Guys I have been getting comments that there are no examples of keys here. If you click on the hyperlink provided below in green colour, you would see the complete separate tutorial of each key with examples.

Primary Key – A primary is a column or set of columns in a table that uniquely identifies tuples (rows) in that table.

Super Key – A super key is a set of one of more columns (attributes) to uniquely identify rows in a table.

Candidate Key – A super key with no redundant attribute is known as candidate key

Alternate Key – Out of all candidate keys, only one gets selected as primary key, remaining keys are known as alternate or secondary keys.

Composite Key – A key that consists of more than one attribute to uniquely identify rows (also known as records & tuples) in a table is called composite key.

Foreign Key – Foreign keys are the columns of a table that points to the primary key of another table. They act as a cross-reference between tables.

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About the Author

I have 15 years of experience in the IT industry, working with renowned multinational corporations. Additionally, I have dedicated over a decade to teaching, allowing me to refine my skills in delivering information in a simple and easily understandable manner.

– Chaitanya

Comments

  1. Kgotso says

    March 14, 2017 at 11:07 AM

    It would really be helpful if there were examples for all the keys using one table to demonstrate them

    Reply
    • Scott says

      June 24, 2018 at 2:14 PM

      You can reach the examples of each by clicking either the hyperlinks on the left or the ones in the web page itself.

      Reply
    • Taslim Arif says

      August 28, 2018 at 6:26 PM

      if u would have clicked on any of key u might have seen all the details mate.

      Reply

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