MySQL ISNULL() Function
The ISNULL() function in MySQL checks if an expression evaluates to NULL (meaning it doesn't have a value). It's a simple but important function for handling missing data.
ISNULL(): Definition and Usage
This function is useful for conditional logic or data validation. It returns 1 if the expression is NULL, and 0 otherwise. It helps you to identify and handle situations where a value might be missing.
Syntax
Syntax
ISNULL(expression)
Parameter Values
| Parameter | Description |
|---|---|
expression |
The value or expression you want to check for NULL. This is required. |
Examples
Testing a NULL Value
This checks if a NULL value is indeed NULL.
Syntax
SELECT ISNULL(NULL);
Output
1
Testing an Empty String
An empty string ("") is *not* considered NULL in MySQL.
Syntax
SELECT ISNULL("");
Output
0
Testing a Numeric Value
A numeric value is also not NULL.
Syntax
SELECT ISNULL(350);
Output
0
Testing a Non-Empty String
A non-empty string is not NULL.
Syntax
SELECT ISNULL("Hello world!");
Output
0