Primary Key


A primary key is a specific field in a database table that is designed to uniquely identify every record in that table. It is a unique identifier, meaning it doesn’t contain any duplicate values, ensuring that each record can be individually identified. A primary key can either be a single field (column) or a combination of fields in a table.


The phonetics of the keyword “Primary Key” is: /ˈpraɪmɛri ki:/

Key Takeaways


  1. A Primary Key is a special relational database table column designated to uniquely identify all the table records. It has values that are unique for each record in the table.
  2. Primary Keys must contain unique values. A primary key column cannot have null values. Each table in a database has one and only one primary key, which is used to identify each record uniquely.
  3. A Primary Key can consist of one or more fields on a table. When multiple fields are used as a primary key, it is known as a composite key. They are important in the normalization of databases as they eliminate redundancy and establish relationships between tables.



The term “Primary Key” is important in the technology field, particularly in database management, because it is a unique identifier for records in an information table. The primary key plays a crucial role in maintaining data integrity and ensuring there’s no duplication. It forms the basis for unique indexes – a vital attribute for efficient data retrieval. By referencing the primary keys, relationships can be created and maintained in the dataset between different tables, thus supporting the concept of relational databases. This helps greatly in normalization and orderly arrangement of data. Therefore, primary keys greatly aid in guaranteeing accurate and efficient database operation.


A primary key primarily serves as a unique identifier for each record in a database table. The primary purpose of this key is to implement an efficient and reliable way to find, sort, and maintain data. Each table in a database can only have one primary key. This ensures that there is no ambiguity or conflict when accessing or manipulating data. It makes certain that no two records or tuples within a table share the same key and thus guarantees the uniqueness and integrity of data.Primary keys also play a pivotal role in the establishment of relationships among different tables in relational databases. They are used to define a ‘one-to-many’ relationship between tables, where the primary key from one table is used as a ‘foreign key’ in another table. This relationship facilitates easy linking and retrieval of data across multiple tables. The primary key’s role in managing database relationships very efficiently underlines its importance in database management systems.


Primary Key is a special relational database concept that uniquely designates a record in a database table. Here are three real-world examples:1. Student Database: In a school database, each student could have a unique ID number (often referred to as a Student ID). This ID serves as the Primary Key for the student’s record in the database. Different students might share the same name, or even the same birthday, but their IDs are always unique, making it possible to easily retrieve and manage the related data.2. Employee Records: In a company’s HR system, every employee is usually assigned a unique Employee ID. This ID serves as the Primary Key in the Employee database. Even if two people have the same name, the system can always use the unique ID to distinguish one from another.3. Banking System: In a bank’s computer system, every account is given a unique Account Number which serves as the Primary Key for that account. This number is used to manage all the transactions, balance, personal information and other related data for a particular account.

Frequently Asked Questions(FAQ)

Q: What is a primary key in technology?A: A primary key is a field in a database that uniquely identifies each record or row in the database table. It is used to guarantee data consistency and to establish relationships between tables in the database.Q: How does a primary key work?A: A primary key works by ensuring that every record in a database table can be uniquely identified. It does this by restricting any two rows from having the same primary key value, thus avoiding potential duplication and confusion.Q: Can a table have more than one primary key?A: No, a table can only have one primary key. However, this key can consist of one or multiple fields which together form a unique identifier for each record in a table, known as a composite key.Q: What is the difference between a primary key and a foreign key?A: A primary key uniquely identifies a record in its own table, while a foreign key is used to link two tables together by matching the primary key in one table with the foreign key in another. Q: Can a primary key contain null values?A: A primary key cannot contain null or undefined values, as it would compromise its ability to uniquely identify each record in a database table.Q: What happens if a primary key is deleted?A: Deleting a primary key could have serious consequences, as it may disrupt the relationships between tables and cause loss of data integrity. This is why changes to the primary key should be done with extreme caution.Q: What is a composite primary key?A: A composite primary key is a type of primary key that consists of multiple fields/columns, as opposed to a single field. This combination of fields is used to create a unique identifier for each record.Q: Are primary keys always numerical?A: No, primary keys can be any data type – such as integers, strings, dates, and more – as long as it can uniquely identify a record. The only requirements are that they must be unique and not null.

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