Salesforce: Custom Button with Javascript

Salesforce custom button with the javascript is a very exciting feature to implement. We received a requirement from our customer for converting Leads. User should convert Lead record only if the status is changed to "Qualified". Typically when a lead is converted, Salesforce automatically changes the lead status to Qualified. But there are some custom validation rules created for lead record which doesn't allow to complete the conversion process and display error message as validation rules on lead page are not fulfilled.

I created a custom "Convert" button with the help of Javascript and replaced with standard button on lead page layout. The javascript validates whether lead status is qualified or not and doesn't allow user to proceed if it is not qualified.

Code:
var status = "{!Lead.Status}";
if (status == "Qualified")
{
window.location = 'https://ap1.salesforce.com/lead/leadconvert.jsp?retURL=%2F{!Lead.Id}&id={!Lead.Id}';
}
else
{
alert('Please change the Lead Status to Qualified then click on convert');
}


Error Message:

Salesforce: Simple Roll-Up Summary Calculation Using Apex Trigger

Roll-up summary is a very useful function in Salesforce. We can calculate Sum, Max, Min and Average of numbers and currencies of child records in a Master-detail relationship. But there are few limitations.

1. Roll-up summaries can be calculated only in Master-Detail relationships. You cannot calculate roll-up summary in Look-Up Relationships.
2. We can have only 10 Roll-up summary fields.
3. There are few standard objects on which we need Roll-Up summary but it's not available. E.g. Roll-up Asset information in Account. Need to know how many Assets are installed for a particular account.
4. You can't use date functions in Roll-up summary calculations.

To overcome these problems we can write a trigger with SOQL select Aggregate functions.

Scenario: I have two objects here. Milestone and effort. In efforts I'm capturing number of hours spent for a particular task. I wish to have a sum of all these efforts related Milestone record.

Here is the sample code:

1:  trigger Sum_Effort_Hours_in_Milestone on Effort__c (after delete, after insert, after update, after undelete) {  
2:  if (Trigger.isDelete)  
3:  {  
4:  for (effort__c E : Trigger.old)  
5:    {  
6:      Milestone__c M = [select name, Milestone_Hours_2__c from Milestone__c where id =:E.Milestone__c];  
7:      List groupedResults = [select sum(Hours__c)aver from Effort__c where Milestone__c =: M.id];  
8:      Decimal decimalRevenue = 0;  
9:      if(groupedResults.size() > 0)
10:      {  
11:        String str = '' + groupedResults[0].get('aver') ;  
12:        decimalRevenue = Decimal.ValueOf(str) ;  
13:        System.debug('decimalRevenue ::::: ' + decimalRevenue) ;  
14:      }  
15:      M.Milestone_Hours_2__c = decimalRevenue;  
16:      update M;  
17:    }  
18:  }  
19:  else  
20:  {  
21:  for (effort__c E : Trigger.new)  
22:    {  
23:      Milestone__c M = [select name, Milestone_Hours_2__c from Milestone__c where id =:E.Milestone__c];  
24:      List groupedResults = [select sum(Hours__c)aver from Effort__c where Milestone__c =: M.id];  
25:      Decimal decimalRevenue = 0;  
26:      if(groupedResults.size() > 0)  
27:      {  
28:        String str = '' + groupedResults[0].get('aver') ;  
29:        decimalRevenue = Decimal.ValueOf(str) ;  
30:        System.debug('decimalRevenue ::::: ' + decimalRevenue) ;  
31:      }  
32:      M.Milestone_Hours_2__c = decimalRevenue;  
33:      update M;  
34:    }  
35:  }  
36:  }  

Hope this will help you in writing some complex triggers. Cheers...!!

Help Articles:
Aggregate Functions
Jeff Douglas - SOQL