To Count numberofcontacts using trigger.We can use RollupSummary for master-detail relationship,but we can create
only 2 master-detail reationships for an object.
1.we have to create a read-only field with number to get count
2.we should create read-only field in parent object.
3.we have to get count from the child object,so we write trigger only child object.
Note:If any queries please comment.
trigger NumberofContacts on contact(after insert,after update,after delete)
{
map<id,integer> mapacc=new map<id,integer>();
list<Account> 1stacc=new list<Account>();
if(trigger.isInsert)
{
for(contact con:trigger.new)
{
integer count=0;
if(mapacc.containskey(con.Accountid))
{
count+=mapacc.get(con.accountid);
}
count++;
mapacc.put(con.Accountid,count);
}
if(!mapacc.isempty())
{
for(Account acc:[select id,name,numberofcontacts__c from Account where id in:mapacc.keyset()])
{
Account a:new Account(id=acc.id);
mapacc.containskey(acc.id);
if(a.numberofcontacts__c!=null)
{
a.numbeeofcontacts__c=acc.numberofcontacts__c+mapacc.get(acc.id);
}
else
{
a.numberofcontacts__c=mapacc.get(acc.id);
}
firstacc.add(a);
}
}
}
if(trigger.isUpdate)
{
for(contact con:trigger.new)
{
integer count=0;
if(mapacc.containskey(con.Accountid))
{
count+=mapacc.get(con.accountid);
}
count++;
mapacc.put(con.Accountid,count);
}
for(contact con:trigger.old)
{
integer count=0;
if(mapacc.containskey(con.Accountid))
{
count+=mapacc.get(con.accountid);
}
count--;
mapacc.put(con.Accountid,count);
}
if(!mapacc.isempty())
{
for(Account acc:[select id,name,numberofcontacts__c from Account where id in:mapacc.keyset()])
{
Account a:new Account(id=acc.id);
mapacc.containskey(acc.id);
if(a.numberofcontacts__c!=null)
{
a.numbeeofcontacts__c=acc.numberofcontacts__c+mapacc.get(acc.id);
}
else
{
a.numberofcontacts__c=mapacc.get(acc.id);
}
firstacc.add(a);
}
}
}
if(trigger.isDelete)
{
for(contact con:trigger.old)
{
integer count=0;
if(mapacc.containskey(con.Accountid))
{
count+=mapacc.get(con.accountid);
}
count--;
mapacc.put(con.Accountid,count);
}
if(!mapacc.isempty())
{
for(Account acc:[select id,name,numberofcontacts__c from Account where id in:mapacc.keyset()])
{
Account a:new Account(id=acc.id);
mapacc.containskey(acc.id);
if(a.numberofcontacts__c!=null)
{
a.numbeeofcontacts__c=acc.numberofcontacts__c+mapacc.get(acc.id);
}
else
{
a.numberofcontacts__c=mapacc.get(acc.id);
}
firstacc.add(a);
}
}
}
if(!firstacc.isempty())
{
update firstacc;
}
}
