SQL NULL Functions

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SQL NULL is a special value that represents the absence of data in a column. It is not equivalent to an empty string or zero, and requires special handling in SQL queries. SQL provides several functions that allow you to work with NULL values in your queries. Some commonly used SQL NULL functions include:

The SQL Server ISNULL() function lets you return an alternative value when an expression is NULL:

 

SELECT ProductName, UnitPrice * (UnitsInStock + ISNULL(UnitsOnOrder, 0))

FROM Products;

IS NULL: The IS NULL operator is used to check if a column contains a NULL value. For example:

SELECT column1, column2

FROM table_name

WHERE column1 IS NULL;

This query will retrieve rows from the table where column1 contains a NULL value.

IS NOT NULL: The IS NOT NULL operator is used to check if a column does not contain a NULL value. For example:

SELECT column1, column2

FROM table_name

WHERE column1 IS NOT NULL;

This query will retrieve rows from the table where column1 does not contain a NULL value.

These are some common SQL NULL functions that you can use to handle NULL values in your SQL queries. Please note that the syntax and usage of NULL functions may vary depending on the specific SQL database management system (DBMS) you are using, as different DBMS may have different implementations and syntax for NULL functions.

 

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