It is not possible to test for NULL values with comparison operators, such as =, <, or <>. We will have to use the IS NULL and IS NOT NULL operators instead. SELECT column_names FROM table_name WHERE column_name IS NULL; SELECT column_names FROM table_name WHERE column_name IS NOT NULL; Below is a selection from the Customers table used in the examples:

typeof null; // "object" (not "null" for legacy reasons) typeof undefined; // "undefined" null === undefined; // false null == undefined; // true null === null; // true null == null; // true !null; // true Number.isNaN(1 + null); // false Number.isNaN(1 + undefined); // true

January 5, 2026 - Attribute Not Applicable: The value is undefined for a specific record. Setting a NULL value is appropriate when the actual value is unknown, or when a value is not meaningful.

June 12, 2018 - The basic rule is simple: null should only be allowed when it makes sense for an object reference to have 'no value associated with it'. (Note: an object reference can be a variable, constant, property (class field), input/output argument, and so on.) For example, suppose type person with fields name and dateOfFirstMarriage:

October 25, 2025 - If a value appears suspiciously often or seems impossible; it might be an attempt to input NULL values. ... Just to name a couple of examples: I once saw a database where all of the customers who made a purchase before 2005 had an age of 27.

July 24, 2026 - A null should not be confused with a value of 0. A null indicates a lack of a value, which is not the same as a zero value. For example, in the question "How many books does Adam own?", the answer may be "zero" (the number of books is known to be zero) or "null" (the number of books is not known).

September 15, 2021 - Use the IS NULL or IS NOT NULL predicate to test for a null value. This can add complexity to the WHERE clause. For example, the TerritoryID column in the AdventureWorks Customer table allows null values.

The null value does not indicate why a value is absent—it simply marks the places that do not have a data value. For example, the SQL language itself uses the null value for the absent values resulting from an outer join.2 Although exceptions exist,3 it is not generally possible to tell why a value is null.

July 25, 2025 - You can use the NULL value itself directly as an operand of an operator or predicate. For example, the (1 = NULL) comparison is supported. This is the same as if you cast NULL to the appropriate data type, as follows: (1 = CAST(NULL AS INT)).

November 12, 2025 - Oracle Database currently treats ... the same as nulls. Any arithmetic expression containing a null always evaluates to null. For example, null added to 10 is null....

There are a number of variations on this. Here are a few of them: The value does exist somewhere, but the database does not have it. The value has not yet been determined, but it presumably will be determined at some point. For example, a customer has yet to make a decision about a feature.

The value is not yet known. Since the NULL values are basically non-existent, you cannot use comparison operators such as = , <, or > with them.

In these examples, COUNT(price) excludes rows with NULL discounts, and SUM(salary) sums only rows with non-NULL bonuses.

September 12, 2024 - For example, assume a column for a middle name is nullable. In this case, NULL values indicate that the person either does not have a middle name or this information has not been provided yet.

You use the keyword NULL to indicate a null value. For example, the following INSERT statement inserts a new row into the DEPARTMENT table. The department number and name and the division code are known, but the department head has not been appointed yet.

March 3, 2020 - When writing queries, there are times that you'll want to filter out rows with NULL values. Other times, you'll specifically want to retrieve rows that contain NULLs. Here's how to do both: Queries can filter out nulls using the IS NOT NULL clause. Here's an example that excludes films from the Sakila database that contain a NULL original_language_id:

Answer (1 of 3): The phrase SQL NULL is used to signify a missing value. In a table, a NULL value is a value in a field that seems to be blank. A field with a NULL value is one that has no value. It is critical to realize that a NULL value is not the same as a zero value or a field that contains...

'' (empty string): An empty text value. Example: name field left blank · Imagine a survey asking for income. NULL means the person skipped the question entirely. Zero means they answered and said they have no income.