Question

I am working in MS WebMatrix using razor.

The issue I am having is that if one of my queries resolves to an error (dividing by 0, for instance) the whole page fails. I want the query to output “0” for this.

Code:

var itot = db.QueryValue("SELECT SUM(SUBTOTAL) from dbo.DR_TRANS where TRANSDATE = 41195 and SUBTOTAL >0");

var ctot = db.QueryValue("SELECT SUM(SUBTOTAL) from dbo.DR_TRANS where TRANSDATE = 41195 and TRANSTYPE = 1 and SUBTOTAL <0");

var nett = itot + ctot;

So, if either itot or ctot renders Null or error because there is no entries for the selected date, how do I get it to treat error as “0” so the math still works? In this example, itot is total invoices raised today, ctot is total credits raised today.

If there are no invoices yet, or if there are no credits raised yet, my code throws an error and shuts the page down. I want it to display 0 if there’s none of either, and the value of itot if theres no ctot.

What am I doing wrong? it works fine the moment there’s some of each, but I want it to work before that, because there’s other code on the page for displaying other query results.

I’m very new to coding queries, so there will be a basic answer I have missed in my online searching!

Answer 1

Wrapping the aggregate function with COALESCE should return 0 rather than NULL:

SELECT COALESCE(SUM(SUBTOTAL), 0)
   FROM dbo.DR_TRANS
   WHERE TRANSDATE = 41195
     AND SUBTOTAL >0

ie a function that returns the first parameter if it is not null, and the second parameter if the first is NULL. I don’t know what function to use with webmatrix, but COALESCE is pretty standard. In Oracle, you could use NVL. ISNULL is another such function.