Explain keys of Database system? Foreign Key, Candidate Key, Primary Key, Super Key, Composite Key, Alternate Key, Surrogate Key, Compound Key, Natural Key

Definition Of Key 


Keys play an important role in the relational database. It is used to uniquely identify any record or row of data from the table. It is also used to establish and identify relationships between tables. KEYS in DBMS is an attribute or set of attributes which helps you to identify a row(tuple) in a relation(table). They allow you to find the relation between two tables. Keys help you uniquely identify a row in a table by a combination of one or more columns in that table. Key is also helpful for finding unique record or row from the table. Database key is also helpful for finding unique record or row from the table.


There are mainly Eight different types of Keys in DBMS and each key has it’s different functionality:


  1. Super Key
  2. Primary Key
  3. Candidate Key
  4. Alternate Key
  5. Foreign Key
  6. Compound Key
  7. Composite Key
  8. Surrogate Key




  • Primary Key: A primary key is a column or set of columns in a table that uniquely identifies each row in the table. It is used to enforce entity integrity, which ensures that each row in a table is unique and can be identified.


  • Foreign Key: A foreign key is a column or set of columns in one table that refers to the primary key of another table. It is used to enforce referential integrity, which ensures that the relationship between two tables is consistent.


  • Candidate Key: A candidate key is a column or set of columns that can be used as a primary key. It is unique and can be used to identify each row in a table.


  • Super Key: A super key is a set of columns that can uniquely identify each row in a table. It is not necessarily minimal and may contain extra columns.


  • Alternate Key: An alternate key is a column or set of columns that can be used as a primary key. It is unique and can be used to identify each row in a table, but it is not currently being used as the primary key.


  • Composite Key: A composite key is a set of columns that, when combined, can uniquely identify each row in a table. It is used when a single column cannot uniquely identify each row.


  • Surrogate Key: A surrogate key is a column or set of columns that is added to a table to serve as the primary key. It is typically an auto-generated value, such as an identity column in SQL Server or a sequence in Oracle.


  • Natural Key: A natural key is a column or set of columns that is unique and can be used as a primary key. It is based on the data itself, rather than an artificially generated value.



FAQ(SAME Answer For these question)


  1. What are the different types of Database keys?
  2. What are the keys of the database management system?
  3. What is the importance of keys in DBMS?
  4. What is a key in SQL?

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