Various keys in DBMS
Database Keys
A database key is a set of attributes that helps to uniquely identify a row in a table. These keys are also used to establish relationships between different tables in the database.
Types of Keys
1. Primary Key
A Primary key is a attribute of a table that helps to identify every record present in that table uniquely. it not allows user to have any null or duplicate values.
2. Candidate Key
A Candidate key have the same properties as the primary keys. and can also uniquely identify any data tuples in the table.
3. Super Key
A Super key is the set of all those columns of a table which are capable of identifying the each rows of a table uniquely.
4. Foreign Key
A Foreign key is an column in a table that acts as a primary key in another table. It is used to establish relationship between two tables.
5. Alternate Key
An Alternate key is a secondary key that contains all the properties to become a primary key but is not selected as a primary key, so considered as alternate key.
6. Composite Key
A Composite key is a combination of two or more columns that helps to identify each tuple in a table uniquely. When columns are considered separately the values of tuple may not be found unique.
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