Null queries

The above interpretation is correct but i would like to give you three different types of interpretations with null value in SQL. Sometimes the user does not know the value of the attribute. To define that attribute value the null value is used.

Sometimes there are scenarios where attributes were used in past but now there is no need of those attributes. These kind of situations the null value is used. I would like to give you the basic mistake of the developers regarding null value in SQL. So may SQL developers are using the! These operators needs to use when there is not null constraint. If there are null values in SQL then user will find wrong results possibly. Until he obtains the number or learns that the customer has no fax at all, the fax entry is null.

A little background Is Null and IsNull both find null values, but you won't use them in the same way. Null is a reserved word and represents a null entry in expressions, but you will seldom use this value alone.

You certainly don't need to enter it as a value. As long as you enter nothing at all, Access assumes a Null value for the entry. In this article, I am using lower case when referring to the general null condition; proper case denotes an actual Null value.

First, to find Null values in the Region field in the Employees table, base a new query on that table and add the LastName and Region fields to the grid. If you enter Null, Access changes it to Is Null for you. The results, shown in Figure B , identify the Null Region values by employee. Tutorials, references, and examples are constantly reviewed to avoid errors, but we cannot warrant full correctness of all content.

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