Primary Key and Foreign Key

The database relationship is a set of joint statements that creates relationships between one or more tables. It’s being used to obtain data from a database quickly. Relationships may be divided into three categories. One-to-One database relationships, One-to-Many database relationships, and Many-to-Many database relationships are the three types of database relationships. A primary key is used to ensure that each column’s value is unique. The foreign key is what connects the two tables together.

Primary Key

A primary key is a precise choice of a basic set of properties that uniquely define a tuple in relation to the relational data model of databases. Informally, a primary key is defined as “which characteristics identify a record,” and in basic circumstances consists of a single attribute: a unique ID.

The Primary key constraint uniquely identifies each entry in a table. Primary keys cannot have NULL values and must have unique values. A table may only have ONE unique identifier, which can be made up of a single or several columns (fields).

Advantages of Employing Primary Key

The following are some of the advantages of employing a primary key:

• The primary key’s principal purpose is to identify each individual entry in the data structure
• When you don’t want anyone to enter null values, you can use the main key
• To ensure data integrity, when you remove or change information, the action you specify will be executed
• Perform a restricted action on the parent table to prevent deleting or updating operations

Foreign Key

A Foreign Key is a data key that is used to connect two tables. The Foreign Key constraint establishes links between database tables by referring to a column or collection of columns in the Child table that includes the foreign key to the Primary key column or grouping of columns in the Parent table. A foreign key is a collection of attributes in one table that relates to the primary key of another table. These two tables are linked via a foreign key.

A foreign key is a group of columns in one table whose contents must match those of another table’s column. Foreign Key restrictions guarantee referential integrity, which means that if column value A refers to column value B, column value B must exist.

Advantages of Employing A Foreign Key

The following are some of the advantages of employing a foreign key: 

• When you use a primary key from the parent database to move entities, foreign keys come in handy
• You can use a foreign key to connect two or more tables
• It ensures that the data in your database is consistent
• In a parent table, a foreign key could be used to compare a column or a group of columns with the main key

Primary Key And Foreign Key: Difference

Primary Key

• The distinctiveness of the table is usually the emphasis of a primary key It ensures that the value in a certain column is unique
• Only one main key is allowed in a table
• Null values are not permitted in the main key
• It can uniquely identify a record in the table  
• The value of the main key cannot be changed from the parent table
• The temporary tables can be used to completely specify the limitation

Foreign Key

• A foreign key is often used to establish a link between two tables
• Tables can have several foreign keys
• Multiple null values can be stored in a foreign key
• A foreign key is a table field that serves as the main key for another table
• The value can then be removed from the child’s table

The regional or global temporary tables cannot be used to specify its limitation.

Conclusion 

We discussed longitudinal waves, transverse waves, the difference between primary key and foreign key, and other related topics through the study material notes on the difference between primary key and foreign key. A Foreign Key is a field (or set of fields) in one database that relates to the Primary Key in another. The table containing the foreign key is referred to as the child table, whereas the table containing the main key is referred to as the reference or parent table.