What is the term for an identifier that references a database column in which each value is unique?

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Multiple Choice

What is the term for an identifier that references a database column in which each value is unique?

The idea being tested is identifying the main row identifier in a table. A primary key is a column (or a set of columns) whose values are unique for every row and cannot be null, making it the primary way to identify a specific record. This unique identifier is what other tables reference with foreign keys to establish relationships, tying data together across the database. A unique constraint also enforces uniqueness, but it doesn’t inherently serve as the row’s official identifier and can allow NULLs in some systems. An index speeds up lookups but isn’t by itself the mechanism for ensuring a row’s uniqueness. A foreign key points to a key in another table to maintain referential integrity, rather than being the unique identifier for rows in the current table.

The idea being tested is identifying the main row identifier in a table. A primary key is a column (or a set of columns) whose values are unique for every row and cannot be null, making it the primary way to identify a specific record. This unique identifier is what other tables reference with foreign keys to establish relationships, tying data together across the database.

A unique constraint also enforces uniqueness, but it doesn’t inherently serve as the row’s official identifier and can allow NULLs in some systems. An index speeds up lookups but isn’t by itself the mechanism for ensuring a row’s uniqueness. A foreign key points to a key in another table to maintain referential integrity, rather than being the unique identifier for rows in the current table.

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