What is the purpose of the SQL IFNULL function?

To replace NULL values with another value in query results, you can utilize the IFNULL function in SQL. The main purpose of the IFNULL function is to check if a field’s value is NULL, and if it is, then it returns the specified replacement value, otherwise it returns the original value of the field.

The purpose of the IFNULL function includes:

1. Handling NULL values: When it is necessary to handle NULL values in the query results, you can use the IFNULL function to replace NULL values with a specified value, making the query results more readable.
2. Return default value: The IFNULL function can be used to set a default value. It returns the specified default value when the query result is empty or NULL, preventing unknown or uncertain situations.
3. Data transformation: In certain cases, it may be necessary to convert NULL values to another value for calculation or comparison, and the IFNULL function can help achieve this goal.

In conclusion, the IFNULL function can easily handle NULL values in query results, improving the accuracy and readability of the results.