Need help on trigger which is used to update parent record when child record value changes

Question

Hi i have written trigger in which SC_Problem_Management__c is parent object and SC_Problem_Case_Link__c is child object having master detail relationship. I want to update status field of parent object to awaiting deployment when all child records status having value as 'Tested'.

trigger updatestatus on SC_Problem_Case_Link__c(after update) {
    List<SC_Problem_Management__c> parentObjList = new List<SC_Problem_Management__c>();
    List<SC_Problem_Management__c> parentObjListToBeUpdated = new List<SC_Problem_Management__c>();
    public List<Id> listIds = new List<Id>();
    for (SC_Problem_Case_Link__c childObj : Trigger.new) {
        listIds.add(childObj.SC_Problem_Management__c);
    }
    parentObjList = [SELECT Id,Status__c, (SELECT ID, Status__c FROM SC_Problem_Case_Link__r) FROM SC_Problem_Management__c WHERE ID IN :listIds];
    Boolean checkApproval = TRUE;
    for (SC_Problem_Management__c bid : parentObjList) {
        for (SC_Problem_Case_Link__c bsaa : bid.SC_Problem_Case_Link__r) {
            if (bsaa.Status__c == 'Tested') {
                checkApproval = TRUE;
            } else {
                checkApproval = FALSE;
            }
        }
        if (checkApproval == TRUE) {
            bid.Status__c = 'Awaiting Deployment';
        }
        parentObjListToBeUpdated.add(bid);
    }
    if (parentObjListToBeUpdated.size() > 0) {
        update parentObjListToBeUpdated;
    }
}

I am getting error while saving the trigger. "Error Error: Compile Error: Status__c,(SELECT ID, Status__c FROM SC_Problem_Case_Link__r) FROM SC_Problem_Management__c ^ ERROR at Row:1:Column:48 Didn't understand relationship 'SC_Problem_Case_Link__r' in FROM part of query call. If you are attempting to use a custom relationship, be sure to append the '__r' after the custom relationship name. Please reference your WSDL or the describe call for the appropriate names. at line 9 column 21"

Please guide on this issue.

Answer 1

Moving the comment to the answer section so that the question can be closed.

You can use Rollup Summary fields since you have a Master-Detail relationship.

You can create a rollup summary field for count of all child records and another field to see the count of child records with status as Tested. When both counts match, a trigger (before update) / WF Rule on the parent can update the status on the parent record.