The SQL ISNULL function can be used to replace null values in the results of a query with alternate data. The ISNULL function
is used by Microsoft SQL. Other SQL platforms, such as Oracle and MySQL use comparable functions such as
NVL, IFNULL and COALESCE.
Employees Table
| employeeID | employeeName | age |
|---|
| 1000 | John Smith | 40 |
| 1001 | Fred White | 27 |
| 1002 | | 53 |
| 1003 | Samuel Williams | 31 |
In this example, when we query the employees table, we want to replace null values in the employeeName field with 'Unknown'.
Syntax
SELECT ISNULL(column_name,'value')
FROM Table |
Example
SELECT ISNULL(employeeName,'Unknown') as [Employee Name]
FROM employees
|
Results
| Employee Name |
|---|
| John Smith |
| Fred White |
| Unknown |
| Samuel Williams |
The SQL ISNULL function can be very helpful when null values need to be replaced in the result set with alternate information.
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