DML, SOQL and DML Sequence

Question

Here is my scenario.

Transaction 1: DML to update the Status field from Open to Closed on ABC record.

Transaction 2: SOQL is performed to retrieve the ABC record before the above DML and updates the price value. Will the Status be Closed or Open after the second DML?

If the status is Open, how can I ensure that Transaction 1 updates are not overwritten in Transaction 2 DML?

Answer 1

Only include the fields you really want to update in the record passed to the DML operation. A perfect way to do that is to not use the record you queried, but construct a new one. For example:

List<ABC__c> abcs = [SELECT Id, A__c, B__c, C__c FROM ABC__c WHERE ...];
List<ABC__c> updatedAbcs = new List<ABC__c>();

for (ABC__c abc : abcs) {
    updatedAbcs.add(new ABC__c(abc.Id, B__c = 'new value'));
}

update updateAbcs;

This way only the B__c field will be updated, leaving all other fields unaffected, even if you queried them in the original SOQL used here.