Oracle NVL2 - SQL

Oracle NVL2 is a function that is used to evaluate an expression to determine if it is null or not. It takes three arguments, the first argument is the expression that is evaluated, the second argument is the value that is returned if the expression is not null, and the third argument is the value that is returned if the expression is null.

Syntax

The syntax for the Oracle NVL2 function is as follows:

NVL2(expression, value_if_expression_not_null, value_if_expression_is_null)

Here, expression is the expression that is evaluated, value_if_expression_not_null is the value that is returned if the expression is not null, and value_if_expression_is_null is the value that is returned if the expression is null.

Example

Let's consider an example to understand the Oracle NVL2 function better. Suppose we have a table employees with the following data:

employee_id  |  first_name  |  last_name  |  salary
---------------------------------------------------
100          |  John        |  Doe        |  5000
101          |  Jane        |  Smith      |  NULL
102          |  Bill        |  Gates      |  10000
103          |  Steve       |  Jobs       |  NULL

Suppose we want to create a report that shows the employee's salary and a message indicating whether the salary is specified or not. We can use the Oracle NVL2 function to accomplish this. The following SQL query will give us the desired result:

SELECT
  employee_id,
  first_name,
  last_name,
  NVL2(salary, 'Salary is ' || salary, 'Salary not specified') AS salary_message
FROM employees;

In this query, we are using the Oracle NVL2 function to evaluate the salary column. If the salary column is not null, the function returns the message 'Salary is ' concatenated with the salary value. If the salary column is null, the function returns the message 'Salary not specified'.

The result of the above query would be:

employee_id  |  first_name  |  last_name  |  salary_message
-----------------------------------------------------------
100          |  John        |  Doe        |  Salary is 5000
101          |  Jane        |  Smith      |  Salary not specified
102          |  Bill        |  Gates      |  Salary is 10000
103          |  Steve       |  Jobs       |  Salary not specified

Conclusion

The Oracle NVL2 function is a useful function that can be used to determine if an expression is null or not. It can be used to simplify complex SQL queries and make them easier to read and understand.