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For loop & query for custom object



I am new at this so please bare with me but I am trying to create an Apex class with a query in a custom object.


The custom Object is called "SIM"



I basically want to use a For loop to sum a field for all records under this object that have the same two fields


The two fields are called:


"Account" which is a masterdetail relationship lookup field to the Standard Account Object

"Item" which is a masterdetail relationship lookup field to a Custom Object called "INV"


However to do this I need to first retrieve the account ID or name.  I tried somehting like this:


String accountId = SIM__c.Account__c.getId();

and I got this error:


ErrorError: Compile Error: Method does not exist or incorrect signature: [Schema.SObjectField].getId()

Any Ideas?


I think the code would be different for the two since one is Master/detail lokup to a standard object and the other to a custom object.  I need help for both of them.


Thanks in advance!!




As account is standard object here is the way you can access acount id


String accountId =;


The account's ID value would be simply the contents of the field:



Id accountId = SIM__c.Account__c;

Lookup fields only appear to reference the name of the record it looks up when using the graphical interface; non-technical users appreciate being able to see John Doe instead of 003X000000aD3Fz when they view a record on their screen or in a report. The Salesforce database always stores just a link to the record (hence the term "lookup field") by using that record's unique ID value; this value is what Apex Code and the API see when you reference the field's value.