I have some data that I would like to split based on a delimiter that may or may not exist.

Example data:

John/Smith
Jane/Doe
Steve
Bob/Johnson

I am using the following code to split this data into First and Last names:

SELECT SUBSTRING(myColumn, 1, CHARINDEX('/', myColumn)-1) AS FirstName,
       SUBSTRING(myColumn, CHARINDEX('/', myColumn) + 1, 1000) AS LastName
FROM   MyTable

The results I would like:

FirstName---LastName
John--------Smith
Jane--------Doe
Steve-------NULL
Bob---------Johnson

This code works just fine as long as all the rows have the anticipated delimiter, but errors out when a row does not:

"Invalid length parameter passed to the LEFT or SUBSTRING function."

How can I re-write this to work properly?