Difference Between Primary key and Foreign key

Introduction

Because it is an effective and dependable way for producing, storing, and maintaining data in databases, database management systems (DBMS) are vital in fields such as commerce, banking, airlines, telecommunications, and universities. RDBMS (Relational Database Management System) is a more sophisticated version of DMBS designed specifically for relational databases. These databases store information in tables with rows and columns that represent entries and attributes, respectively.

What exactly is a primary key?

A primary key is a group of columns that determines the set of rows in a table in a unique way. A candidate key is a single characteristic with a unique ID that is also referred to as a main key. A simple primary key and a composite primary key are the two sorts of primary keys. A database table with just one column has a simple primary key, while a database table with many columns has a composite primary key.

Because the primary key defines a significance in the database, its value should never vary or be modified. As a consequence, altering the value would cause a lot of confusion. So that no one can identify the data in that table, the primary key should not have a null value at the start. Furthermore, no two rows will have the same primary key since the database would not be unique. As a result, each row of data in a table can only have one primary key.

Because the primary key is cluster-indexed, all of the table's rows are sorted. A temporary table is used to define the primary key. When removing rows from a table, it's important to make sure the removed value isn't present in the foreign key column.

What exactly is a foreign key?

A foreign key is a column in a database table that connects two tables together. This property is the foreign key when table 1 has a primary key from table 2. The foreign key in table 1 is known as the referring key, while the main key in table 2 is known as the referenced relation.

Foreign keys, unlike primary keys, may have null values since they don't assist identify a difference in the connection because primary keys have already done it. Foreign keys, unlike primary keys, may allow duplicate values and a database can have many or many foreign keys since foreign keys might have distinct qualities. Foreign keys, on the other hand, cannot have clustered indexes.

On a temporary table, foreign keys cannot be defined. When adding a value to a foreign key column, ensure sure the value is present in the main key, and delete entries from a foreign key with no constraints. Foreign tables aid in preserving the database's table integrity. The database management system can prevent any value from being accidentally deleted.

Comparison Table Between Primary Key and Foreign Key

Conclusion

In a database management system, keys play a vital role in creating associations both inside and across tables. However, in order to do so, we must ensure that the areas used to establish linkages across tables have similar values and that the table contains unique rows.

This article discusses the two most important and frequent keys that make relational database management systems perform effectively by creating relationships between tables. Primary keys and foreign keys are discussed in length and distinguished to assist people realize how distinct they are from one another. This is because, despite their similar appearances, these words serve different purposes.