The ISNULL function replaces NULL values with a specified value.
This function is a short-hand for a CASE expression.
ISNULL is used to replace NULL with a more meaningful value.
This example replaces NULL with the a double-dash value.
SELECT CompanyName, ISNULL(Fax, '--') AS Fax
FROM Supplier
| CompanyName | Fax |
|---|---|
| Exotic Liquids | -- |
| New Orleans Cajun Delights | -- |
| Grandma Kelly's Homestead | (313) 555-3349 |
| Tokyo Traders | -- |
| Cooperativa de Quesos 'Las Cabras' | -- |
 |
|
As you can see, when Fax is NULL, it is replaced with '--'.
Syntax of the ISNULL function.
ISNULL(value, replacement-value)
value -- a value or column name (which is checked for NULL).
replacement-value -- a value to replace the NULL value with.
| SUPPLIER |
|---|
| Id |
| CompanyName |
| ContactName |
| City |
| Country |
| Phone |
| Fax |
SELECT CompanyName, ISNULL(Fax, 'Phone: ' + Phone) AS Contact
FROM Supplier
| CompanyName | Contact |
|---|---|
| Exotic Liquids | Phone: (171) 555-2222 |
| New Orleans Cajun Delights | Phone: (100) 555-4822 |
| Grandma Kelly's Homestead | (313) 555-3349 |
| Tokyo Traders | Phone: (03) 3555-5011 |
| Cooperativa de Quesos 'Las Cabras' | Phone: (98) 598 76 54 |
|
|
