allUsers.get(a.OwnerID); is returning null

Question

trigger userDetailupdateFromAccount on Account (before update) {

    //Get all accounts
    Map<ID,Account> acc = new Map<ID,Account>([Select OwnerID,Name FROM Account WHERE ID IN : Trigger.oldMap.keyset()]);
    //Get all users
    Map<ID,user> allUsers = new Map<ID,User>([Select ID,Name,email from User where ID IN : acc.keyset()]);
    Map<ID,User> accToUser = new Map<ID,User>();
    for(Account a : trigger.new){
        User u = allUsers.get(a.OwnerID);
      //  a.description__c = u.Email;
      system.debug('zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz'+allUsers+acc );
      system.debug('xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx'+acc.keyset());
    }    
}

Map acc = new Map([Select OwnerID,Name FROM Account WHERE ID IN : Trigger.oldMap.keyset()]); - is setting AccountID to Map. How can I assign it to OwnerID instead of AccountID ?

Thanks

Answer 1

You don't need to query to get the immediate fields of the Account so your trigger can look like this:

trigger userDetailupdateFromAccount on Account (before update) {

    Set<Id> owners = new Set<Id>();
    for (Account a : Trigger.new) {
        owners.add(a.OwnerId);
    }

    Map<ID,user> users = new Map<ID,User>([
            Select ID,Name,email
            from User
            where ID IN :owners
            ]);

    for (Account a : Trigger.new) {
        User u = users.get(a.OwnerID);
        ...
    }
}