The database constraint that ensures all values in a column are different is called ________.
- SSLV
- NFTs
- TDMA
- UNIQUE
Answer: UNIQUE
UNIQUE constraint enforces that all values in a column (or column combination) are distinct across rows. Unlike PRIMARY KEY, UNIQUE allows NULL values (typically one NULL per column). Used for business keys like email, phone number. Multiple UNIQUE constraints can exist per table, aiding data integrity and query optimization.