We are using the SQL query:
Select tank from lookuptanks where projectedTank = ‘{Root Container.TankSelected}’
The problem is that sometimes there is no value in TankSelected, so there is nothing returned from SQL. We are looking for NULL or a tank number from this query. I tried using the Fallback Value and putting null in there, but it returned the string ‘null’ instead. Is there a good way to get a null back?
No, there is no way to specify a “null” fallback value. Either use an invalid tank number (e.g. -1) as a fallback, or write a query like this:
(SELECT tank FROM lookuptanks WHERE projectedTank = '{Root Container.TankSelected}')
UNION
(SELECT null)
This way, if the first query returns no rows, you’ll get the result from the second query, but if the first query returns a value, you’ll get that. This works because binding a scalar value (anything but a DataSet) to a query uses column 0 row 0 from the result.