As you cannot edit the SELECT portion of the SQL statement in Crystal, the above wouldn't work. As well, the value for b.field would still be null, as appending another value to the result set wouldn't alter the value of b.field.
SELECT a.somefield, b.field
FROM Table1 AS a LEFT JOIN Table2 AS b ON a.field = b.field
Instead, create a formula in Crystal check for a null value, and replace the null value with your default.
//Assumes {b.field} is a string
If IsNull({b.field}) then 'default value
Else {b.field}
There are other ways to solve this, including the use of SQL Expressions, views, stored procs, but this formula based solution will work with any database driver. Malcolm Wynden
Authorized Crystal Engineer
malcolm@wynden.net