What is the PostgreSQL equivalent for ISNULL()

How do I emulate the ISNULL() functionality ?

SELECT (Field IS NULL) FROM ...

Use COALESCE() instead:

SELECT COALESCE(Field,'Empty') from Table;

It functions much like ISNULL, although provides more functionality. Coalesce will return the first non null value in the list. Thus:

SELECT COALESCE(null, null, 5); 

returns 5, while

SELECT COALESCE(null, 2, 5);

returns 2

Coalesce will take a large number of arguments. There is no documented maximum. I tested it will 100 arguments and it succeeded. This should be plenty for the vast majority of situations.

SELECT CASE WHEN field IS NULL THEN 'Empty' ELSE field END AS field_alias

Or more idiomatic:

SELECT coalesce(field, 'Empty') AS field_alias

Try:

SELECT COALESCE(NULLIF(field, ''), another_field) FROM table_name