Question

Here is my code:

SELECT CASHIER_ID AS SERVER, CONVERT(VARCHAR(10),[DATETIME],111) AS DATE, 
  SUM(GRAND_TOTAL) AS TOTAL_SALES, 
  SUM(NUM_PEOPLE_PARTY) AS NUMBER_SERVED,  
  SUM(GRAND_TOTAL) / SUM(NUM_PEOPLE_PARTY) AS CASHPERCUSTOMER 
FROM INVOICE_TOTALS 
WHERE [DATETIME] >= '2012-06-01' 
GROUP BY CASHIER_ID, CONVERT(VARCHAR(10),[DATETIME],111)  

Everything works perfect with the code except for the:

SUM(GRAND_TOTAL) / SUM(NUM_PEOPLE_PARTY) AS CASHPERCUSTOMER

portion. If I take this line out then everything works perfect, If I put it in I receive the following error:

Message: Could not retrieve datatable.

SELECT CASHIER_ID AS SERVER, …rest of query above…

Stack Trace:
…irrelevant stack trace…

Message: Divide by zero error encountered.

Stack Trace:
…irrelevant stack trace…

This is SQL inside a restaurant point-of-sale (POS) system that uses SQL Server. Any ideas why this may be occuring?

Answer 1

Check for 0 before dividing:

SELECT
    ...,
    CASE WHEN SUM(NUM_PEOPLE_PARTY) = 0
         THEN NULL
         ELSE SUM(GRAND_TOTAL) / SUM(NUM_PEOPLE_PARTY) END AS CASHPERCUSTOMER,
    ... 

Or get the same result by using NULLIF:

SELECT
    ...,
    CASE SUM(GRAND_TOTAL) / NULLIF(SUM(NUM_PEOPLE_PARTY), 0) AS CASHPERCUSTOMER,
    ...