Keys

A key is a column or group of columns that uniquely identifies each row in a table.

Keys have the following functions in a database:

• Data Integrity - Enforces uniqueness and prevents duplicates.
• Relationships - Connects data across tables.
• Indexing - Accelerates query performance and data retrieval.

There are several different types of keys:

• Primary Key
• Foreign Key
• Candidate Key
• Unique Key
• Super Key
• Composite Key
• Alternate Key
• Natural Key
• Surrogate Key