SQL查询：使用带有左联接的聚合函数时，不应为NULL的NULL值

Question

i dont have much expiriance with SQL and i am trying to crack my head on this query. i have 3 tables: Projects, Calculator and partialBilling (note: the 'calculator' columns you see at the code ive added 'k','l','m' etc are real...i didnt gave them those names...).

the query is working fine but part of the values that i am expecting from the aggregate function ('sumofTotal' column) are returning as null values and and they should not be null. I would be grateful if someone point out the mistake in the query.

SELECT Projects.SpCall,Projects.CustName,Projects.CustNumber
,Projects.ReceiveDate,Projects.StartDate,Projects.ProjectType
,Calculator.AN,Projects.Professional,Projects.PmUserName
,Projects.AcountManager,Projects.CrmCallNum,Projects.ProjectCategory
,Projects.CallNum,Projects.ContactName,Projects.ContactPhone
,Projects.ContactEmail,Projects.HiddenNote,Projects.RowColor
, Projects.HeaderCellText,
 SUM(Calculator.K + Calculator.L + Calculator.M + Calculator.N + Calculator.AD + Calculator.AR) AS sumofTotal
 ,partialBilling.Ammount FROM Projects LEFT JOIN Calculator ON Projects.SpCall=Calculator.AQ
  LEFT JOIN partialBilling ON Projects.SpCall = partialBilling.spCall
   WHERE PmUserName= 'JOHN DOE'AND OpertionalStatus
    <> 'Billed' AND OpertionalStatus<> 'Finished' AND
     OpertionalStatus<> 'Passed To Billing' AND OpertionalStatus<> 'Scanning' 
     AND OpertionalStatus<> 'Ended' 
     AND OpertionalStatus<> 'Green Billing' 
     AND (GeneralStatus= 'Passed To Project Manager' 
     OR GeneralStatus= 'Astrategic Project') 
     GROUP BY Projects.SpCall,Projects.CustName,Projects.CustNumber
     ,Projects.ReceiveDate,Projects.StartDate,Projects.ProjectType
     ,Calculator.AN,Projects.Professional,Projects.PmUserName
     ,Projects.AcountManager,Projects.CrmCallNum,Projects.ProjectCategory
     ,Projects.CallNum,Projects.ContactName,Projects.ContactPhone
     ,Projects.ContactEmail,Projects.HiddenNote,Projects.RowColor
     , Projects.HeaderCellText,partialBilling.Ammount;

Answer 1

尝试使用IFNULL（）

SUM(IFNULL(Calculator.K,0) + ... + IFNULL(Calculator.AR,0)) AS sumofTotal

Answer 2

Instead of proprietary IFNULL better use Standard SQL COALESCE :

SUM(COALESCE(Calculator.K,0) + COALESCE(Calculator.L,0), ...`

Or maybe a bit more efficient:

SUM(COALESCE(Calculator.K,0)) + SUM(COALESCE(Calculator.L,0)), ...`

Answer 3

您可以使用ifnull('column_name' , '')类的表达式代替column_name 。