It is responsible for managing the relationship between the tables. Let us now understand the Syntax of creating the table with the Primary key specified.Ī Foreign key is beneficial when we connect two or more tables so that data from both can be put to use parallelly.Ī foreign key is a field or collection of fields in a table that refers to the Primary key of the other table. Similarly, when we talk about employees in a company, the employee ID is functioning as the Primary key for identification.
A Primary key can never take NULL values.įor example, in the case of a student when identification needs to be done in the class, the roll number of the student plays the role of Primary key. The primary key column has a unique value and doesn’t store repeating values. What is a Primary Key in SQL?Ī Primary key is a unique column we set in a table to easily identify and locate data in queries. Let us now dive into the concept of Primary and Foreign keys by understanding the definition, syntax, and examples of both keys. A foreign key comes to use when we need to link tables to one another and have data spread over multiple tables. When we talk about Foreign key, we can have as many Foreign keys as we want. The primary key is limited to a single table and is put to uniquely identify the corresponding rows of a table. Both the Primary and the foreign key are SQL constraints.Ĭonstraints in SQL help us to manage the data and avoid any invalid transactions on it. In this tutorial, we will look at the concept of Primary and foreign key.
#MYSQL FOREIGN KEY FREE#
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