A field identified in a table as holding the unique identifier of the table’s records is called the

A field identified in a table as holding the unique identifier of the table’s records is called the: 1) foreign key 2) unique ID 3) candidate key 4) primary key

The correct answer and explanation is:

The correct answer is: 4) primary key

Explanation:

In database terminology, a primary key is a field (or a set of fields) in a table that uniquely identifies each record (or row) within that table. The primary key ensures that no two records have the same value in this field, maintaining the uniqueness of each entry.

Why the Primary Key?

• Uniqueness: The primary key guarantees that each record can be uniquely identified. For example, in a table of employees, an employee ID can be the primary key because each employee has a unique ID number.
• Not Null: A primary key field cannot contain null values because it must always hold a value to identify a record.
• Indexing: Primary keys are often automatically indexed to allow fast retrieval of records based on the key.
• Relationship: In relational databases, primary keys are critical for creating relationships between tables (through foreign keys).

What about the other options?

1. Foreign Key:
   A foreign key is a field (or set of fields) in one table that refers to the primary key in another table. It establishes a link between the data in the two tables, enforcing referential integrity, but it is not used to uniquely identify records in its own table.
2. Unique ID:
   While the term “unique ID” might colloquially refer to any field with unique values, it is not a formal database term. The concept is essentially captured by the primary key, but “unique ID” is not the correct technical term.
3. Candidate Key:
   Candidate keys are fields or sets of fields that could potentially be primary keys because they also uniquely identify records. However, only one candidate key is chosen to be the primary key. The others remain candidate keys or might be declared unique keys.

Summary:

The primary key is the designated unique identifier for each record in a database table. It ensures data integrity and supports efficient data retrieval. Foreign keys link tables, candidate keys are potential primary keys, and “unique ID” is a generic, informal term.

If you’re designing or querying a database, identifying the primary key is essential for structuring the data correctly and ensuring its reliability and consistency.