Key

✅ Key

identify the tuples(rows) uniquely in the table

🔑 Candidate Key

minimal set to uniquely identify a tuple every table must have at least single candidate key can have multiple candidate keys can be null

• student number
• student phone number
• student name

🔑 Primary Key

one of many candidate keys only one per table can never be null

🔑 Super Key

set of attirbutes to uniquely identify a tuple

• set {student number, phone number, name}

🔑 Alternate Key

any other candidate key except primary key

🔑 Foreign key

key refereneced from another table