FUNDAMENTALS OF COMPUTER

Detailed explanation-1: -A primary key consists of one or more fields that uniquely identify each record that you store in the table. Often, there is a unique identification number, such as an ID number, a serial number, or a code, that serves as a primary key.

Detailed explanation-2: -The primary key is accepted as a unique or sole identifier for every record in the table. In the case of a primary key, we cannot save NULL values. In the case of a unique key, we can save a null value, however, only one NULL value is supported.

Detailed explanation-3: -Primary Key-a field containing a value that uniquely identifies each record in a table. The primary key is unique and prevents entering duplicate records or a null value in that field. Foreign Key-a key in a related table that refers to the primary key in another table.

Detailed explanation-4: -A primary key, also called a primary keyword, is a column in a relational database table that’s distinctive for each record. It’s a unique identifier, such as a driver’s license number, telephone number with area code or vehicle identification number (VIN). A relational database must have only one primary key.

Detailed explanation-5: -Often, a unique identification number, such as an ID number or a serial number or code, serves as a primary key in a table. For example, you might have a Customers table where each customer has a unique customer ID number. The customer ID field is the primary key.