Different Types of Keys in DBMS

Keys in DBMS:

DBMS Keys are a data item that exclusively identifies a record. There are six different types of keys in DBMS:

Example: Account_number, Employee_number and customer_number uses as DBMS Keys because it specific identify a record store in a database.

Types of Keys in DBMS:

In DBMS, There are six types of keys are exists:

1. Super Key:

A Super key for an entity is a set of one or more attributes whose combined value uniquely identifies the entity in the entity set. Superset of any candidate key is also says Super key.

2. Primary Key:

The primary key uniquely identifies each record in a table and must never be the same for two records.

3. Candidate Key:

A candidate key is an attribute or a set of attributes that it identifies a record uniquely. These attributes or combinations of attributes say candidate keys.

4. Composite Key:

A composite key is a group of fields that it combines to uniquely identify a record. When we design a database, we will have tables that will use more than one column as a part of the primary key. So, it says a composite key or concatenated key.

5. Foreign Key:

In relation, the column whose data values correspond to the values of a key column in another relation says a Foreign Key.

6. Secondary Key:

A secondary key is an attribute or combination of attributes that may not be a candidate key but classifies the entity set on a particular characteristic. A table can have multiple choices for a primary key but only one can be set as the primary key. All the keys are not the primary key that says Secondary Key.