Exploring PostgreSQL ISNULL Alternatives: A Quick Overview

PostgreSQL doesn’t include the ISNULL function, common in other SQL dialects. This article briefly explores suitable alternatives within PostgreSQL that achieve similar functionality.

PostgreSQL ISNULL Alternatives While PostgreSQL lacks ISNULL, it offers other ways to handle NULL values. For instance, the COALESCE function returns the first non-NULL value from a list:

-- PostgreSQL
SELECT COALESCE(salary, 0) AS salary 
FROM employee;

Similarly, the CASE statement can mimic ISNULL’s behavior:

-- PostgreSQL
SELECT CASE WHEN salary IS NULL THEN 0 ELSE salary END AS salary 
FROM employee;

FAQ

What is the difference between ISNULL and COALESCE?

COALESCE is a standard SQL function that returns the first non-NULL value, whereas ISNULL’s behavior varies by SQL dialect.

Why doesn’t PostgreSQL support ISNULL?

ISNULL isn’t part of the standard SQL specifications, and PostgreSQL adheres closely to these standards.

Can COALESCE handle multiple arguments?

Yes, COALESCE can handle multiple arguments and returns the first non-NULL value among them, offering greater flexibility than ISNULL.

Is the CASE statement a viable alternative to ISNULL in PostgreSQL?

Absolutely, the CASE statement in PostgreSQL can mimic the behavior of ISNULL by providing conditional checks for NULL values, allowing for complex logical constructs.

Conclusion

Though PostgreSQL does not support ISNULL directly, alternatives like COALESCE and CASE statements effectively replace it. For more in-depth insights please read PostgreSQL ISNULL: The Missing Function.