|SQL - Structured Query Language|
NOT NULL Constraint
NULL is a unique mark in the SQL that indicate data value does not exist in the Database. NULL concept was introduced by Dr.E.F. Codd to represent missing data in the Relational Database Model. By default, all columns can store with NULL data value in the Relational Database. NOT NULL Constraint is used define in the mandatory column that absolutely needs data value.
The following SQL Statements are used to create DEPT and EMP Tables with set of constraints.
More Reference URL: https://data-e-education.com/RDBMS/Domain_Integrity_Constraints.php
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