@isTest (seeAllData = true)
public class SOQLqueries {
static testMethod void SOQLandCollections(){
        //This only works when this test Class is set to SeeAllData=True!
        List<Account> accts = [Select ID from Account];
        System.debug(accts.size());
        System.debug(accts);
        //System.debug(accts[0].Name);//This won't work because Name was not acquired in the query.

        accts = [Select ID, Name, Phone, BillingState from Account];
        System.debug(accts.size());
        System.debug(accts);
        System.debug(accts[0].Name);

        List<Contact> cons = [Select Department, MobilePhone, IsDeleted from Contact];
        System.debug(cons);
        System.debug('smashing****************************' + cons[0].Id);


        //Populating a Map from a SOQL Query is also easy, although not as intutive
        //Note that you have to "cast" the query results (a List) to a Map
    	Map<Id, Account> acctMap1 = new Map<Id, Account>([Select ID, Name from Account]);
    	System.debug('Account Map: ' + acctMap1);

    	Map<Id, Contact> conMap1 = new Map<Id, Contact>(cons);
        System.debug(conMap1);
        Map<Id, Contact> conMap2 = new Map<Id, Contact>([Select Id, Department, MobilePhone, IsDeleted from Contact]);
        System.debug(conMap2);


        //COMMON ROOKIE ERROR
        //Using Lists to update record instead of Maps
        List<Account> acctList = [Select ID, Name, Industry, Ownership from Account];
        List<Account> acctListToUpdate = new List<Account>();

        //{Some logic here that determines Type must be updated on a record}
        acctList[0].Type = 'Retailing';
        acctListToUpdate.add(acctList[0]);

        //{Some other logic here that determines Rating must be updated on the same record}
        acctList[0].Rating = 'Super Hot';
        acctListToUpdate.add(acctList[0]);

        System.debug(acctList[0]);

        System.debug(acctListToUpdate);
        /* The update below compiles: you can save this class with it uncommented, but the class
         * fails when we run the test because we added the same record to the list twice.
         */
        //update acctListToUpdate;//Fails with "Duplicate id in list" exception.


        //Let's try the same thing, but using a Map to hold the records to be updated
        Map<ID, Account> acctMapToUpdate = new Map<Id, Account>();

        //We make the same field/values assigment as before on the same record
        acctList[0].Type = 'Mineral Extraction';
        //but now we put the record in a Map instead of a list
        acctMapToUpdate.put(acctList[0].Id, acctList[0]);

        //And we do it again for the Rating Field
        acctList[0].Rating = 'Heavy';
        //when we put it a second time, the Map recognizes that the ID already exists, and just
        //amends the data in the Map with the new information
        acctMapToUpdate.put(acctList[0].Id, acctList[0]);

        system.debug(acctMapToUpdate);
        update acctMapToUpdate.values();

        //Here's an unexpected pattern for SOQL queries with Parent & Child records
        //You would expect that it might be a List<List> pattern so you could call Contacts
        //with acctsCons[0][0] but instead you must use dot notation to reference the sub-lists
        List<Account> acctCons = [SELECT Name, (SELECT FirstName, LastName FROM Contacts) FROM Account];
     	system.debug(acctCons[0].Contacts[0].FirstName);

    }
}