Explain the use of DML merge operation in Salesforce?

Hi Laveena,

The merge statement merges up to three records of the same sObject type into one of the records, deleting the others, and re-parenting any related records.

The following example merges two accounts named 'Acme Inc.' and 'Acme' into a single record:

List<Account> ls = new List<Account>{new Account(name='Acme Inc.'),new Account(name='Acme')};
insert ls;
Account masterAcct = [SELECT Id, Name FROM Account WHERE Name = 'Acme Inc.' LIMIT 1];
Account mergeAcct = [SELECT Id, Name FROM Account WHERE Name = 'Acme' LIMIT 1];
try {
    merge masterAcct mergeAcct;
} catch (DmlException e) {
    // Process exception here
}