Trigger to prevent creating duplicate accounts in salesforce

This post explains how to prevent creating duplicate accounts in Salesforce.

Trigger :

trigger Prevent_duplicacy on Account (before insert) {

  Set<string> str=new Set<string>();

    for(Account acc:trigger.new)

    {

        str.add(acc.name);

    }

    

    List<Account> acc= new List<Account>([select name from Account where name in:str]);

    

    for(Account a:trigger.new)

    {

        if(acc.size()>0)

        {

            a.adderror('error');

        }

    }

}

As I already have an account named Microsoft in my org.. When I am trying to create a new account with same the name it shows an error.

Thanks,

 Lovesalesforceyes