How to resolve the issue of the nvl function not working in Oracle?

If the NVL function in Oracle is not functioning properly, it may be due to incorrect parameter passing or an error in the function call. Before resolving this issue, you can try the following methods:

1. Check if the parameters are passed correctly: Ensure that the number and types of parameters passed to the NVL function are correct. The NVL function takes two parameters, the first parameter being the value to check and the second parameter being the default value to return when the first parameter is empty.
2. Replace with COALESCE function: The COALESCE function can achieve similar functionality to the NVL function and can also handle multiple parameters. When using the COALESCE function, set the first parameter as the value to check, and subsequent parameters as the default values to return when the first parameter is empty.
3. Check the database version and permissions to ensure that the database version supports the NVL function and that the user has sufficient permissions to use the function.

If the above methods fail to solve the problem, you can try rewriting the query statement or contacting the database administrator for further investigation and repair.