During my schooling, one of my teachers said, “A friend of mine scored 105 on a science test out of 100. I was wondering how it is possible to score 105 out of 100. In this case, the value was inflated. Later, it was revealed that the score was a miscalculation. His score was 97. In some contexts, there is a range of values defined, and no value should exceed the defined range.”

The same concept applies to check constraints in SQL Server. Let us consider the age of an employee as an integer data type for a column in an employee table. One of the employees has entered the number -76 (negative 76) in the Age column. In the context of age, it is not possible to have age in a negative number. SQL server will not raise any error because negative values are acceptable in an integer data type. To prevent this, the Age column should accept only positive numbers. This can be accomplished by adding a check constraint on the Age column for the employee table. Let’s get started.