MySQL provides a set of constraints that you can include in your table definitions to help ensure the integrity of the data. The constraints let you better control the types of data that can be added to the database. For example, you can use constraints to set a column’s uniqueness or nullability, specify a default value for a column, or verify that the data falls within a certain range of acceptable values.
MySQL supports six basic types of constraints for ensuring data integrity: PRIMARY KEY, NOT NULL, DEFAULT, CHECK, UNIQUE, and FOREIGN KEY. In this article, I introduce you to