FUNDAMENTALS OF COMPUTER

Detailed explanation-1: -A primary key is the column or columns that contain values that uniquely identify each row in a table. A database table must have a primary key for Optim to insert, update, restore, or delete data from a database table.

Detailed explanation-2: -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-3: -A primary key is a field or set of fields with values that are unique throughout a table. Values of the key can be used to refer to entire records, because each record has a different value for the key. Each table can only have one primary key.

Detailed explanation-4: -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-5: -A field used to access a specific record is called a key. A key is an attribute (or group of properties) that allows us to uniquely identify a row (or tuple) in a table (or relation). A unique identifier is any field that does this. The primary key is the field that is commonly used in any relational database.