// Create the account sObject
Account acct = new Account(Name='Acme', Phone='(415)555-1212', NumberOfEmployees=100);
// Insert the account by using DML
insert acct;
// Get the new ID on the inserted sObject argument
ID acctID = acct.Id;
// Display this ID in the debug log
System.debug('ID = ' + acctID);
// Debug log result (the ID will be different in your case)
// DEBUG|ID = 001D000000JmKkeIA

// Create a list of contacts
List<Contact> conList = new List<Contact> {
    new Contact(FirstName='Joe',LastName='Smith',Department='Finance'),
        new Contact(FirstName='Kathy',LastName='Smith',Department='Technology'),
        new Contact(FirstName='Caroline',LastName='Roth',Department='Finance'),
        new Contact(FirstName='Kim',LastName='Shain',Department='Education')};
// Bulk insert all contacts with one DML call
insert conList;
// List to hold the new contacts to update
List<Contact> listToUpdate = new List<Contact>();
// Iterate through the list and add a title only
//   if the department is Finance
for(Contact con : conList) {
    if (con.Department == 'Finance') {
        con.Title = 'Financial analyst';
        // Add updated contact sObject to the list.
        listToUpdate.add(con);
    }
}
// Bulk update all contacts with one DML call
update listToUpdate;

upsert sObject | sObject[]

upsert sObject | sObject[] field
// upsert sObjectList Account.Fields.MyExternalId;

Contact jane = new Contact(FirstName='Jane',
                         LastName='Smith',
                         Email='jane.smith@example.com',
                         Description='Contact of the day');
insert jane;
// 1. Upsert using an idLookup field
// Create a second sObject variable.
// This variable doesn’t have any ID set.
Contact jane2 = new Contact(FirstName='Jane',
                         LastName='Smith',
                         Email='jane.smith@example.com',
                         Description='Prefers to be contacted by email.');
// Upsert the contact by using the idLookup field for matching.
upsert jane2 Contact.fields.Email;
// Verify that the contact has been updated
System.assertEquals('Prefers to be contacted by email.',
                   [SELECT Description FROM Contact WHERE Id=:jane.Id].Description);

Contact[] contactsDel = [SELECT Id FROM Contact WHERE LastName='Smith'];
delete contactsDel;

try {
        // This causes an exception because
        //   the required Name field is not provided.
        Account acct = new Account();
        // Insert the account
        insert acct;
        } catch (DmlException e) {
        System.debug('A DML exception has occurred: ' +
        e.getMessage());
        }

Database.insert(recordList, false);

Database.SaveResult[] results = Database.insert(recordList, false);

// Create a list of contacts
List<Contact> conList = new List<Contact> {
        new Contact(FirstName='Joe',LastName='Smith',Department='Finance'),
        new Contact(FirstName='Kathy',LastName='Smith',Department='Technology'),
        new Contact(FirstName='Caroline',LastName='Roth',Department='Finance'),
        new Contact()};
// Bulk insert all contacts with one DML call
Database.SaveResult[] srList = Database.insert(conList, false);
// Iterate through each returned result
for (Database.SaveResult sr : srList) {
    if (sr.isSuccess()) {
        // Operation was successful, so get the ID of the record that was processed
        System.debug('Successfully inserted contact. Contact ID: ' + sr.getId());
    } else {
        // Operation failed, so get all errors
        for(Database.Error err : sr.getErrors()) {
            System.debug('The following error has occurred.');
            System.debug(err.getStatusCode() + ': ' + err.getMessage());
            System.debug('Contact fields that affected this error: ' + err.getFields());
	 }
    }
}

Account acct = new Account(Name='SFDC Account');
insert acct;
// Once the account is inserted, the sObject will be
// populated with an ID.
// Get this ID.
ID acctID = acct.ID;
// Add a contact to this account.
Contact mario = new Contact(
    FirstName='Mario',
    LastName='Ruiz',
    Phone='415.555.1212',
    AccountId=acctID);
insert mario;

// Query for the contact, which has been associated with an account.
Contact queriedContact = [SELECT Account.Name
                          FROM Contact
                          WHERE FirstName = 'Mario' AND LastName='Ruiz'
                          LIMIT 1];
// Update the contact's phone number
queriedContact.Phone = '(415)555-1213';
// Update the related account industry
queriedContact.Account.Industry = 'Technology';
// Make two separate calls
// 1. This call is to update the contact's phone.
update queriedContact;
// 2. This call is to update the related account's Industry field.
update queriedContact.Account;

public class AccountHandler {
    public static Account insertNewAccount(String name) {
        try {            
            Account acct = new Account();
            acct.Name = name;
            insert acct;
            
            return acct;
        } catch (DmlException e) {
            System.debug('A DML exception has occurred: ' +
            e.getMessage());
            
            return null;
        }
        
    }
}