How to resolve the issue when Oracle NVL() function isn’t working?

If the NVL() function of Oracle is not functioning properly, the following considerations can be taken to resolve the issue:

1. Check the parameter types of the function: Ensure that the types of the two parameters in the NVL() function are consistent. If the types are not consistent, appropriate type conversion functions can be used for conversion.
2. Check if the function parameters are NULL: Ensure that the first parameter of the NVL() function is not NULL. If the first parameter is NULL, the function will return the second parameter.
3. Check the way the function is called: make sure the NVL() function is called correctly. The syntax of the function is NVL(expr1, expr2), where expr1 is the expression being checked and expr2 is the value returned when expr1 is NULL.
4. Check database connection and permissions: Ensure that the database connection is functioning properly and that the user has appropriate permissions for the tables and columns. If there are any issues with the connection or permissions, it may cause the NVL() function to not work correctly.

If the above methods still do not solve the problem, more specific information can be provided such as function call code, parameter types, and sample data to better help solve the problem.