What Is Not-Null Constraint?

A not-null constraint is a limitation that can be put on a column in relational database tables. This constraint prevents an empty value from being stored in the column. It ensures that the requirement that every row of data in that column must include a value and that during operations to insert or update data, the column cannot be left blank. Additionally, it ensures that the requirement that the column cannot be left blank during operations to insert or update data. If no value is entered for this column, an error message will be issued, and the process of adding new data or changing existing data will not be successful. Take, for example, a table in the bank database designated "CUSTOMER MASTER" that stores information on the bank's clients. Before making a purchase, customers must identify themselves as belonging to a specific gender and give at least one of their surnames. Additionally, they must offer at least one surname. You will then be able to define as "NOT NULL" the two columns that deal with the surname and gender of the client while you are creating the Customer Master database. These columns include information about the customer. A not-null constraint is a valuable tool that database designers have at their disposal to ensure that business logic is adhered to. They leverage a feature already built into the database rather than developing code to enforce the "must always have a value" notion rather than employing the "must always have a value" strategy. This allows them to avoid the need to write additional code. There are several situations in which the validity of the not-null criteria is taken for granted. If a column is designated as the primary key for a database, this indicates that it will be used to generate a singular identification for each entry in the database. This can only happen if the column is unique. As a consequence of this, it is not feasible for any of the rows in the table to be empty.