有人可以幫助我簡化/加快此功能嗎？

Question

該函數根據每月的設定值計算保險費。

以下是我昨晚想到的。我知道這是骯髒和可怕，但它我可以與我目前的知識做了最好的..

declare @january decimal(6,3) 
declare @february decimal(6,3) 
declare @march decimal(6,3) 
declare @april decimal(6,3) 
declare @may decimal(6,3) 
declare @june decimal(6,3) 
declare @july decimal(6,3) 
declare @august decimal(6,3) 
declare @september decimal(6,3) 
declare @october decimal(6,3) 
declare @november decimal(6,3) 
declare @december decimal(6,3) 

set @january = (select earningvalue from tblearningpatterns where clientname = @client and earningpattern = @pattern and calmonth = 'january') 
set @february = (select earningvalue from tblearningpatterns where clientname = @client and earningpattern = @pattern and calmonth = 'february') 
set @march = (select earningvalue from tblearningpatterns where clientname = @client and earningpattern = @pattern and calmonth = 'march') 
set @april = (select earningvalue from tblearningpatterns where clientname = @client and earningpattern = @pattern and calmonth = 'april') 
set @may = (select earningvalue from tblearningpatterns where clientname = @client and earningpattern = @pattern and calmonth = 'may') 
set @june = (select earningvalue from tblearningpatterns where clientname = @client and earningpattern = @pattern and calmonth = 'june') 
set @july = (select earningvalue from tblearningpatterns where clientname = @client and earningpattern = @pattern and calmonth = 'july') 
set @august = (select earningvalue from tblearningpatterns where clientname = @client and earningpattern = @pattern and calmonth = 'august') 
set @september = (select earningvalue from tblearningpatterns where clientname = @client and earningpattern = @pattern and calmonth = 'september') 
set @october = (select earningvalue from tblearningpatterns where clientname = @client and earningpattern = @pattern and calmonth = 'october') 
set @november = (select earningvalue from tblearningpatterns where clientname = @client and earningpattern = @pattern and calmonth = 'november') 
set @december = (select earningvalue from tblearningpatterns where clientname = @client and earningpattern = @pattern and calmonth = 'december') 

set @tripearnings = 1 - @pretripearnings 


if @triptype = '1' 
    begin 
     if datepart(month, @outdate) = 1 
      begin 
       if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 1 
        set @earnedpremium = @premium * (@january /100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 2 
        set @earnedpremium = @premium * ((@january + @february)/100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 3 
        set @earnedpremium = @premium * ((@january + @february + @march) /100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 4 
        set @earnedpremium = @premium * ((@january + @february + @march + @april)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 5 
        set @earnedpremium = @premium * ((@january + @february + @march + @april + @may)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 6 
        set @earnedpremium = @premium * ((@january + @february + @march + @april + @may + @june)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 7 
        set @earnedpremium = @premium * ((@january + @february + @march + @april + @may + @june + @july)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 8 
        set @earnedpremium = @premium * ((@january + @february + @march + @april + @may + @june + @july + @august)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 9 
        set @earnedpremium = @premium * ((@january + @february + @march + @april + @may + @june + @july + @august + @september)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 10 
        set @earnedpremium = @premium * ((@january + @february + @march + @april + @may + @june + @july + @august + @september + @october)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 11 
        set @earnedpremium = @premium * ((@january + @february + @march + @april + @may + @june + @july + @august + @september + @october + @november)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 12 
        set @earnedpremium = @premium 
      end 
     if datepart(month, @outdate) = 2 
      begin 
       if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 1 
        set @earnedpremium = @premium * (@February /100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 2 
        set @earnedpremium = @premium * ((@february + @march)/100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 3 
        set @earnedpremium = @premium * ((@february + @march + @April)/100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 4 
        set @earnedpremium = @premium * ((@february + @march + @april + @may)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 5 
        set @earnedpremium = @premium * ((@february + @march + @april + @may + @june)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 6 
        set @earnedpremium = @premium * ((@february + @march + @april + @may + @june + @july)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 7 
        set @earnedpremium = @premium * ((@february + @march + @april + @may + @june + @july + @august)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 8 
        set @earnedpremium = @premium * ((@february + @march + @april + @may + @june + @july + @august + @september)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 9 
        set @earnedpremium = @premium * ((@february + @march + @april + @may + @june + @july + @august + @september + @october)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 10 
        set @earnedpremium = @premium * ((@february + @march + @april + @may + @june + @july + @august + @september + @october + @november)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 11 
        set @earnedpremium = @premium * ((@february + @march + @april + @may + @june + @july + @august + @september + @october + @november + @december)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 12 
        set @earnedpremium = @premium 
      end 
     if datepart(month, @outdate) = 3 
      begin 
       if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 1 
        set @earnedpremium = @premium * (@march /100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 2 
        set @earnedpremium = @premium * ((@march + @april)/100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 3 
        set @earnedpremium = @premium * ((@march + @April + @may) /100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 4 
        set @earnedpremium = @premium * ((@march + @april + @may + @june)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 5 
        set @earnedpremium = @premium * ((@march + @april + @may + @june + @july)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 6 
        set @earnedpremium = @premium * ((@march + @april + @may + @june + @july + @august)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 7 
        set @earnedpremium = @premium * ((@march + @april + @may + @june + @july + @august + @september)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 8 
        set @earnedpremium = @premium * ((@march + @april + @may + @june + @july + @august + @september + @october)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 9 
        set @earnedpremium = @premium * ((@march + @april + @may + @june + @july + @august + @september + @october + @november)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 10 
        set @earnedpremium = @premium * ((@march + @april + @may + @june + @july + @august + @september + @october + @november + @december)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 11 
        set @earnedpremium = @premium * ((@march + @april + @may + @june + @july + @august + @september + @october + @november + @december + @January)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 12 
        set @earnedpremium = @premium 
      end 
     if datepart(month, @outdate) = 4 
      begin 
       if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 1 
        set @earnedpremium = @premium * (@april /100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 2 
        set @earnedpremium = @premium * ((@april + @may)/100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 3 
        set @earnedpremium = @premium * ((@April + @may + @june) /100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 4 
        set @earnedpremium = @premium * ((@april + @may + @june + @july)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 5 
        set @earnedpremium = @premium * ((@april + @may + @june + @july + @august)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 6 
        set @earnedpremium = @premium * ((@april + @may + @june + @july + @august + @september)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 7 
        set @earnedpremium = @premium * ((@april + @may + @june + @july + @august + @september + @october)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 8 
        set @earnedpremium = @premium * ((@april + @may + @june + @july + @august + @september + @october + @november)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 9 
        set @earnedpremium = @premium * ((@april + @may + @june + @july + @august + @september + @october + @november + @december)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 10 
        set @earnedpremium = @premium * ((@april + @may + @june + @july + @august + @september + @october + @november + @december + @january)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 11 
        set @earnedpremium = @premium * ((@april + @may + @june + @july + @august + @september + @october + @november + @december + @January + @February)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 12 
        set @earnedpremium = @premium 
      end 
     if datepart(month, @outdate) = 5 
      begin 
       if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 1 
        set @earnedpremium = @premium * (@may /100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 2 
        set @earnedpremium = @premium * ((@may + @june)/100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 3 
        set @earnedpremium = @premium * ((@may + @june + @july)/100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 4 
        set @earnedpremium = @premium * ((@may + @june + @july + @august)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 5 
        set @earnedpremium = @premium * ((@may + @june + @july + @august + @september)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 6 
        set @earnedpremium = @premium * ((@may + @june + @july + @august + @september + @october)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 7 
        set @earnedpremium = @premium * ((@may + @june + @july + @august + @september + @october + @november)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 8 
        set @earnedpremium = @premium * ((@may + @june + @july + @august + @september + @october + @november + @december)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 9 
        set @earnedpremium = @premium * ((@may + @june + @july + @august + @september + @october + @november + @december + @january)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 10 
        set @earnedpremium = @premium * ((@may + @june + @july + @august + @september + @october + @november + @december + @january + @february)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 11 
        set @earnedpremium = @premium * ((@may + @june + @july + @august + @september + @october + @november + @december + @January + @February + @march)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 12 
        set @earnedpremium = @premium 
      end 
     if datepart(month, @outdate) = 6 
      begin 
       if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 1 
        set @earnedpremium = @premium * (@june /100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 2 
        set @earnedpremium = @premium * ((@june + @july)/100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 3 
        set @earnedpremium = @premium * ((@june + @july + @august)/100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 4 
        set @earnedpremium = @premium * ((@june + @july + @august + @september)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 5 
        set @earnedpremium = @premium * ((@june + @july + @august + @september + @october)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 6 
        set @earnedpremium = @premium * ((@june + @july + @august + @september + @october + @november)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 7 
        set @earnedpremium = @premium * ((@june + @july + @august + @september + @october + @november + @december)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 8 
        set @earnedpremium = @premium * ((@june + @july + @august + @september + @october + @november + @december + @january)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 9 
        set @earnedpremium = @premium * ((@june + @july + @august + @september + @october + @november + @december + @january + @february)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 10 
        set @earnedpremium = @premium * ((@june + @july + @august + @september + @october + @november + @december + @january + @february + @march)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 11 
        set @earnedpremium = @premium * ((@june + @july + @august + @september + @october + @november + @december + @January + @February + @march + @april)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 12 
        set @earnedpremium = @premium 
      end 
     if datepart(month, @outdate) = 7 
      begin 
       if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 1 
        set @earnedpremium = @premium * (@july /100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 2 
        set @earnedpremium = @premium * ((@july + @august)/100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 3 
        set @earnedpremium = @premium * ((@july + @august + @september)/100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 4 
        set @earnedpremium = @premium * ((@july + @august + @september + @october)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 5 
        set @earnedpremium = @premium * ((@july + @august + @september + @october + @november)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 6 
        set @earnedpremium = @premium * ((@july + @august + @september + @october + @november + @december)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 7 
        set @earnedpremium = @premium * ((@july + @august + @september + @october + @november + @december + @january)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 8 
        set @earnedpremium = @premium * ((@july + @august + @september + @october + @november + @december + @january + @february)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 9 
        set @earnedpremium = @premium * ((@july + @august + @september + @october + @november + @december + @january + @february + @march)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 10 
        set @earnedpremium = @premium * ((@july + @august + @september + @october + @november + @december + @january + @february + @march + @april)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 11 
        set @earnedpremium = @premium * ((@july + @august + @september + @october + @november + @december + @January + @February + @march + @april + @may)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 12 
        set @earnedpremium = @premium 
      end 
     if datepart(month, @outdate) = 8 
      begin 
       if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 1 
        set @earnedpremium = @premium * (@august /100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 2 
        set @earnedpremium = @premium * ((@august + @september)/100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 3 
        set @earnedpremium = @premium * ((@august + @september + @october)/100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 4 
        set @earnedpremium = @premium * ((@august + @september + @october + @november)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 5 
        set @earnedpremium = @premium * ((@august + @september + @october + @november + @december)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 6 
        set @earnedpremium = @premium * ((@august + @september + @october + @november + @december + @january)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 7 
        set @earnedpremium = @premium * ((@august + @september + @october + @november + @december + @january + @february)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 8 
        set @earnedpremium = @premium * ((@august + @september + @october + @november + @december + @january + @february + @march)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 9 
        set @earnedpremium = @premium * ((@august + @september + @october + @november + @december + @january + @february + @march + @april)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 10 
        set @earnedpremium = @premium * ((@august + @september + @october + @november + @december + @january + @february + @march + @april + @may)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 11 
        set @earnedpremium = @premium * ((@august + @september + @october + @november + @december + @January + @February + @march + @april + @may + @june)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 12 
        set @earnedpremium = @premium 
      end 
     if datepart(month, @outdate) = 9 
      begin 
       if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 1 
        set @earnedpremium = @premium * (@september /100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 2 
        set @earnedpremium = @premium * ((@september + @october)/100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 3 
        set @earnedpremium = @premium * ((@september + @october + @november)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 4 
        set @earnedpremium = @premium * ((@september + @october + @november + @december)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 5 
        set @earnedpremium = @premium * ((@september + @october + @november + @december + @january)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 6 
        set @earnedpremium = @premium * ((@september + @october + @november + @december + @january + @february)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 7 
        set @earnedpremium = @premium * ((@september + @october + @november + @december + @january + @february + @march)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 8 
        set @earnedpremium = @premium * ((@september + @october + @november + @december + @january + @february + @march + @april)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 9 
        set @earnedpremium = @premium * ((@september + @october + @november + @december + @january + @february + @march + @april + @may)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 10 
        set @earnedpremium = @premium * ((@september + @october + @november + @december + @january + @february + @march + @april + @may + @june)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 11 
        set @earnedpremium = @premium * ((@september + @october + @november + @december + @January + @February + @march + @april + @may + @june + @july)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 12 
        set @earnedpremium = @premium 
      end 
     if datepart(month, @outdate) = 10 
      begin 
       if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 1 
        set @earnedpremium = @premium * (@october /100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 2 
        set @earnedpremium = @premium * ((@october + @november)/100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 3 
        set @earnedpremium = @premium * ((@october + @november + @december)/100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 4 
        set @earnedpremium = @premium * ((@october + @november + @december + @january)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 5 
        set @earnedpremium = @premium * ((@october + @november + @december + @january + @february)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 6 
        set @earnedpremium = @premium * ((@october + @november + @december + @january + @february + @march)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 7 
        set @earnedpremium = @premium * ((@october + @november + @december + @january + @february + @march + @april)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 8 
        set @earnedpremium = @premium * ((@october + @november + @december + @january + @february + @march + @april + @may)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 9 
        set @earnedpremium = @premium * ((@october + @november + @december + @january + @february + @march + @april + @may + @june)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 10 
        set @earnedpremium = @premium * ((@october + @november + @december + @january + @february + @march + @april + @may + @june + @july)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 11 
        set @earnedpremium = @premium * ((@october + @november + @december + @January + @February + @march + @april + @may + @june + @july + @august)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 12 
        set @earnedpremium = @premium 
      end 
     if datepart(month, @outdate) = 11 
      begin 
       if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 1 
        set @earnedpremium = @premium * (@november /100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 2 
        set @earnedpremium = @premium * ((@november + @december)/100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 3 
        set @earnedpremium = @premium * ((@november + @december + @january)/100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 4 
        set @earnedpremium = @premium * ((@november + @december + @january + @february)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 5 
        set @earnedpremium = @premium * ((@november + @december + @january + @february + @march)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 6 
        set @earnedpremium = @premium * ((@november + @december + @january + @february + @march + @april)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 7 
        set @earnedpremium = @premium * ((@november + @december + @january + @february + @march + @april + @may)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 8 
        set @earnedpremium = @premium * ((@november + @december + @january + @february + @march + @april + @may + @june)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 9 
        set @earnedpremium = @premium * ((@november + @december + @january + @february + @march + @april + @may + @june + @july)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 10 
        set @earnedpremium = @premium * ((@november + @december + @january + @february + @march + @april + @may + @june + @july + @august)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 11 
        set @earnedpremium = @premium * ((@november + @december + @January + @February + @march + @april + @may + @june + @july + @august + @september)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 12 
        set @earnedpremium = @premium 
      end 
     if datepart(month, @outdate) = 12 
      begin 
       if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 1 
        set @earnedpremium = @premium * (@december /100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 2 
        set @earnedpremium = @premium * ((@december + @january)/100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 3 
        set @earnedpremium = @premium * ((@december + @january + @february)/100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 4 
        set @earnedpremium = @premium * ((@december + @january + @february + @march)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 5 
        set @earnedpremium = @premium * ((@december + @january + @february + @march + @april)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 6 
        set @earnedpremium = @premium * ((@december + @january + @february + @march + @april + @may)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 7 
        set @earnedpremium = @premium * ((@december + @january + @february + @march + @april + @may + @june)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 8 
        set @earnedpremium = @premium * ((@december + @january + @february + @march + @april + @may + @june + @july)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 9 
        set @earnedpremium = @premium * ((@december + @january + @february + @march + @april + @may + @june + @july)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 10 
        set @earnedpremium = @premium * ((@december + @january + @february + @march + @april + @may + @june + @july + @august)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 11 
        set @earnedpremium = @premium * ((@december + @January + @February + @march + @april + @may + @june + @july + @august + @september)/ 100) 
       else if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 12 
        set @earnedpremium = @premium 
      end 
    end 

Answer 1

試試這個

set @tripearnings = 1 - @pretripearnings 

if @triptype = '1' 
begin 
    if round((datediff(day, @outdate, @experiencedate)/30.41),0) = 12 
     set @earnedpremium = @premium 
    else 
    begin 
     ;with cte as (
      -- this cte generates data for all 12 months, and then copies them again to make months 13-24 
      -- the "months" 13-24 make calculation easier, because whe you ask for Aug to Apr the next year 
      -- the range is simply months 8 to 16 
      select mth=itr+month('1 ' + calmonth + ' 2010'), earningvalue 
      from tblearningpatterns, (select itr=0 union all select 12) x 
      where clientname = @client and earningpattern = @pattern and isdate('1 ' + calmonth + ' 2010')=1 
     ) 
     select @earnedpremium = @premium * (
      (
      select sum(earningvalue) 
      from cte 
      where mth between month(@outdate) and month(@outdate)+round((datediff(day, @outdate, @experiencedate)/30.41),0)-1 
      )/100) 
    end 
end