Category: Key

A composite key in MySQL is a combination of two or more than two columns in a table that allows us to identify each row of the table uniquely. It is a type of candidate key which is formed by more than one column. MySQL guaranteed the uniqueness of the column only when they are combined. If…

The foreign key is used to link one or more than one table together. It is also known as the referencing key. A foreign key matches the primary key field of another table. It means a foreign key field in one table refers to the primary key field of the other table. It identifies each row of…

MySQL primary key is a single or combination of the field, which is used to identify each record in a table uniquely. If the column contains primary key constraints, then it cannot be null or empty. A table may have duplicate columns, but it can contain only one primary key. It always contains unique value into a…

A unique key in MySQL is a single field or combination of fields that ensure all values going to store into the column will be unique. It means a column cannot stores duplicate values. For example, the email addresses and roll numbers of students in the “student_info” table or contact number of employees in the “Employee”…