Dereference SObject Field from List to Set

Question

After creating the Sobject below, I'm trying to create 3 sets, 1 for YearNumber, Scheduled_Days and MonthNumber to use in a query. I need these 3 sets to be of Integer/String type so I must dereference the SObject field first. I would appreciate help in writing this as it seems as if it should be easy but I've not been doing it right and getting syntax errors.

List schconnList = [select id, Address_Type__c, Address_Type_r.Provider_c, Address_Type_r.Address_c,Schedule_Development__r.Scheduled_Days__c, Schedule_Development_r.YearNumber_c, Schedule_Development_r.MonthNumber_c, Schedule_Development__r.Start_Time__c, Schedule_Development__r.End_Time__c from Schedule_Connection__c where Id in:schconnections];

Set MonthNumber
Set Scheduled_Days
Set YearNumber

Note: I'm creating 3 Sets to later do a query against another Custom Setting using these values. Currently it's querying the entire recordset of this object = BAD so I'm trying to limit this query by using these Sets.

Can I use List to add all items to set in SOQL without loop similar to:
Set yearList = New Set ( [select Schedule_Development_r.YearNumber_c from Schedule_Connection__c where Id in:schconnList].Schedule_Development_r.YearNumber_c.intvalue());

Answer 1

assuming that the Schedule_Development_r.MonthNumber_c and Schedule_Development_r.YearNumber_c fields are of type number, the following should do the trick

Set<String> scheduled_Days = new Set<String>();
Set<Integer> monthNumber = new Set<Integer>();
Set<Integer> yearNumber = new Set<Integer>();

List<Schedule_Connection__c> schconnList = [select id, Address_Type__c, Address_Type_r.Provider_c, Address_Type_r.Address_c,Schedule_Development__r.Scheduled_Days__c, Schedule_Development_r.YearNumber_c, Schedule_Development_r.MonthNumber_c, Schedule_Development__r.Start_Time__c, Schedule_Development__r.End_Time__c from Schedule_Connection__c where Id in:schconnections];

for (Schedule_Connection__c record:schconnList){

  scheduled_Days.add(record.Schedule_Development__r.Scheduled_Days__c);

  if (record.Schedule_Development__r.MonthNumber_c != null){
    monthNumber.add(record.Schedule_Development__r.MonthNumber_c.intValue());
  }

  if (record.Schedule_Development__r.YearNumber_c != null){
    yearNumber.add(record.Schedule_Development__r.YearNumber_c.intValue());
  }

}