Question

I have a project that can use either SQL Server or MS Access as the data store. In one SELECT statement, I must perform a COALESCE operation on a single column and a single value, like this:

SELECT COALESCE([Amount], 0) FROM PaymentsDue;

I would like to write a single SQL statement that will execute correctly in both SQL Server and MS Access. The SQL Server version that is of immediate interest is 2008, although a solution applicable across versions would be preferred.

Earlier today, someone was able to show me an SQL trick that allowed me to use a single SELECT statement to effectively CAST a DATETIME to DATE. I was wondering if anyone has a similar trick to perform a COALESCE (eg, IFNULL or NZ) operation in a way that can be applied to both SQL Server and MS Access?

Answer 1

This will work, but it’s clunky:

SELECT Amount 
FROM PaymentsDue
WHERE Amount IS NOT NULL
UNION ALL
SELECT 0 AS Amount 
FROM PaymentsDue
WHERE Amount IS NULL

Obviously if you have more than one column, this gets to be quickly unmanageable.