What is the unique identifier for a row called? Natural Primary Secondary Foreign
The correct answer and explanation is:
The correct answer is Primary key.
A primary key is a unique identifier for each row in a database table. It ensures that every record can be uniquely identified, which is essential for organizing and accessing data efficiently. No two rows in a table can have the same primary key value, making it unique.
A primary key is usually a single column but can also be a combination of multiple columns. It must contain unique values, and it cannot contain null values because a null would mean the absence of a value, which breaks the rule of uniqueness.
There are different types of keys related to database tables:
- Natural key is a key that comes from the data itself, like a Social Security Number or an email address, which naturally identifies a row.
- Primary key is the main key chosen to uniquely identify rows. It may be natural or created specifically for this purpose.
- Secondary key is not unique and is used mainly for searching or indexing purposes.
- Foreign key is a field (or fields) in one table that refers to the primary key in another table, creating a relationship between the two tables.
Primary keys are fundamental to relational databases. They allow easy retrieval, updating, and deletion of records. Without a primary key, it would be difficult to guarantee data integrity because multiple rows could be identical, causing confusion and errors during data operations.
Database management systems often enforce primary key constraints automatically. This means they will not allow duplicate or null values in the primary key column. This enforcement helps maintain consistency and reliability of the stored data.
In summary, the primary key is the unique identifier for a row in a table, critical for ensuring that each record can be distinctly and reliably accessed within a database system.