In the realm of Database Management Systems (DBMS), keys play a pivotal role in ensuring data integrity and establishing relationships between tables. They serve as unique identifiers for records or rows within a table, facilitating efficient data retrieval and manipulation. Let’s delve into the various types of keys:
1)Candidate Key:
- Candidate keys are the minimal sets of attributes that can uniquely identify a row in a table.
- Unlike primary keys, a table can have multiple candidate keys.
- Each candidate key uniquely identifies a record within the table.
2)Super Key:
- A super key is a set of attributes that can uniquely identify a tuple within a table.
- It may include more attributes than necessary to uniquely identify a tuple.
- Every candidate key is a super key, but not every super key is a candidate key.
3)Primary Key:
- A primary key is a unique and non-null key that identifies a record uniquely within a table.
- Each table can have only one primary key.
- It serves as the primary means of identifying records within the table.
4) Alternate Key:
- Alternate keys are candidate keys other than the primary key.
- They are alternative options for uniquely identifying records within the table.
5)Composite Key:
- A composite key consists of two or more attributes combined to uniquely identify a tuple within a table.
- It offers a more intricate means of identifying records, utilizing multiple attributes.
5)Foreign Key:
- A foreign key is a column or combination of columns in one table that references the primary key in another table.
- It establishes relationships between tables, enforcing referential integrity.
Understanding these key concepts is crucial for designing efficient and normalized databases. By selecting and defining keys, database administrators ensure data accuracy, consistency, and integrity, laying the foundation for robust database systems.