What is the function of the isnull function in Oracle?

In Oracle, there is no function like ISNULL in SQL Server. However, you can use the NVL function to achieve similar functionality.

The purpose of the NVL function is to determine if an expression is NULL, and return a specified value if the expression is NULL, or return the expression itself if it is not NULL.

The grammar is as follows:

NVL(expr1, expr2)

expr1 is the expression to check for NULL, expr2 is the value to return if expr1 is NULL.

For example:

SELECT NVL(salary, 0) FROM employees;

The above query will return the values in the salary column of the employees table, and if the value in the salary column is NULL, it will return 0.