SELECT crm_Customer_Employee_Assignments.CustomerNum, crm_customerPurchaseRollup.custLevel, sum(custsls.priceextension) as sales
FROM crm_Customer_Employee_Assignments
LEFT OUTER JOIN CUSTSLS ON crm_Customer_Employee_Assignments.CustomerNum=CUSTSLS.CustNum
LEFT OUTER JOIN crm_customerPurchaseRollup ON crm_Customer_Employee_Assignments.CustomerNum = crm_customerPurchaseRollup.trueCustNum
WHERE sales>=1.23 group by customernum
Try this:
SELECT crm_Customer_Employee_Assi
FROM crm_Customer_Employee_Assi
LEFT OUTER JOIN CUSTSLS ON crm_Customer_Employee_Assi
LEFT OUTER JOIN crm_customerPurchaseRollup
HAVING SUM(CUSTSLS.PRICEEXTENSION