The UNIQUE constraint ensures that all values in a specified column are distinct across the table. This means that no two rows can have the same value in that column.
For example, if you have a users table with a username column defined as UNIQUE, attempting to insert a new user with a username that already exists will result in an error. This constraint is useful for maintaining data integrity, especially for fields like email addresses or usernames that should be unique identifiers.
If you have more questions about constraints or database design, feel free to ask!
