What’s the diff btw primary key and foreign key?
The main difference between primary key and foreign key is that the primary key is used to identify the records in the table uniquely while the foreign key is used to connect two tables together. What’s the diff btw primary key and foreign key?
Most of the business organizations use databases to store data. A database management system (DBMS) is software that helps create and manage data in databases. An advanced type of DBMS is called a Relational Database Management System (RDBMS). It is based on the relational model. They store data in tables. Each table consists of rows and columns. A row represents an entry, while a column represents an attribute. Tables in RDBMS have an association between them. Keys help identify relationships between tables and uniquely identify any row of data within a table. A key can be a single attribute or a combination of keys. These are various types of keys, and primary key and foreign key are two of them.
Key Areas Covered
1. What is the primary key?
– Definition, Functionality
2. What is the foreign key?
– Definition, Functionality
3. What is the difference between primary key and foreign key?
– Comparison of key differences
What is a primary key? What’s the diff btw primary key and foreign key?
A primary key column in the table helps identify each row or record in the table. Contains unique values. The primary key column cannot have null values. A table can have only one primary key. In a student table, the student_id is the primary key. In a Patient_Details table, patient_id is the primary key. The primary key does not need to have only one field. It can also be a combination of multiple fields as well. When a primary key consists of multiple fields, it is called a composite key. For example, the primary key of the student table can be the combination of student_id and name.
What is a foreign key?
A foreign key is used to refer to another table. It is also called a reference key. It is a column or combination of columns that matches a primary key in a different table. In other words, a foreign key on the table is a primary key of another table.
For example, suppose there is a sales database. It has tables of clients and products. The customer table has columns customer_id, name, address, and contact_no. The primary key of the customer table is customer_id. Product has product_id, name, quality columns. The primary key of the products table is product_id. Placing the product_id in the customer table will create a link between the two tables. The product_id in the products table is the primary key, but it is a foreign key in the customer_table. Similarly, it is possible to connect the tables in the database using the foreign key.
Difference Between Primary Key and Foreign Key
Definition What’s the diff btw primary key and foreign key?
In the relational model of databases, a primary key is a specific choice of a minimal set of attributes or columns that uniquely specify a tuple or row in a table. A foreign key is a field or collection of fields in a table that uniquely identifies a row in another table or the same table. Thus, this constitutes the basic difference between primary key and foreign key.
Number of related tables
The primary key relates to a single table, while a foreign key relates to two tables. So, derived from the basic concept, this is another difference between primary key and foreign key.
null values
Also, a primary key value cannot be null, but a foreign key value can be null.
Duplicate values What’s the diff btw primary key and foreign key?
Also, another difference between primary key and foreign key is that primary key values cannot have duplicate values while foreign key values can have duplicate values.
number of keys
Also, another important difference between primary key and foreign key is that there can only be a single primary key in a table. However, there can be multiple foreign keys in a table.
Use
The primary key is used to uniquely identify the records in the table, while the foreign key is used to link two tables. This is the main difference between primary key and foreign key.
conclusion
Primary key and foreign key are two types of keys used in RDBMS. The difference between primary key and foreign key is that the primary key is used to uniquely identify the records in the table while the foreign key is used to connect two tables together.