##Instruction:
Database: hospital_1
Total Tables: 15
Total Columns: 68

Table Schemas:

hospital_1 contains tables such as Physician, Department, Affiliated_With, Procedures, Trained_In, Patient, Nurse, Appointment, Medication, Prescribes, Block, Room, On_Call, Stay, Undergoes.
Table Physician has columns such as EmployeeID, Name, Position, SSN.
EmployeeID is the primary key.
Table Department has columns such as DepartmentID, Name, Head.
DepartmentID is the primary key.
Table Affiliated_With has columns such as Physician, Department, PrimaryAffiliation.
Physician is the primary key.
Table Procedures has columns such as Code, Name, Cost.
Code is the primary key.
Table Trained_In has columns such as Physician, Treatment, CertificationDate, CertificationExpires.
Physician is the primary key.
Table Patient has columns such as SSN, Name, Address, Phone, InsuranceID, PCP.
SSN is the primary key.
Table Nurse has columns such as EmployeeID, Name, Position, Registered, SSN.
EmployeeID is the primary key.
Table Appointment has columns such as AppointmentID, Patient, PrepNurse, Physician, Start, End, ExaminationRoom.
AppointmentID is the primary key.
Table Medication has columns such as Code, Name, Brand, Description.
Code is the primary key.
Table Prescribes has columns such as Physician, Patient, Medication, Date, Appointment, Dose.
Physician is the primary key.
Table Block has columns such as BlockFloor, BlockCode.
BlockFloor is the primary key.
Table Room has columns such as RoomNumber, RoomType, BlockFloor, BlockCode, Unavailable.
RoomNumber is the primary key.
Table On_Call has columns such as Nurse, BlockFloor, BlockCode, OnCallStart, OnCallEnd.
Nurse is the primary key.
Table Stay has columns such as StayID, Patient, Room, StayStart, StayEnd.
StayID is the primary key.
Table Undergoes has columns such as Patient, Procedures, Stay, DateUndergoes, Physician, AssistingNurse.
Patient is the primary key.
The Head of Department is the foreign key of EmployeeID of Physician.
The Department of Affiliated_With is the foreign key of DepartmentID of Department.
The Physician of Affiliated_With is the foreign key of EmployeeID of Physician.
The Treatment of Trained_In is the foreign key of Code of Procedures.
The Physician of Trained_In is the foreign key of EmployeeID of Physician.
The PCP of Patient is the foreign key of EmployeeID of Physician.
The Physician of Appointment is the foreign key of EmployeeID of Physician.
The PrepNurse of Appointment is the foreign key of EmployeeID of Nurse.
The Patient of Appointment is the foreign key of SSN of Patient.
The Appointment of Prescribes is the foreign key of AppointmentID of Appointment.
The Medication of Prescribes is the foreign key of Code of Medication.
The Patient of Prescribes is the foreign key of SSN of Patient.
The Physician of Prescribes is the foreign key of EmployeeID of Physician.
The BlockFloor of Room is the foreign key of BlockFloor of Block.
The BlockCode of Room is the foreign key of BlockCode of Block.
The BlockFloor of On_Call is the foreign key of BlockFloor of Block.
The BlockCode of On_Call is the foreign key of BlockCode of Block.
The Nurse of On_Call is the foreign key of EmployeeID of Nurse.
The Room of Stay is the foreign key of RoomNumber of Room.
The Patient of Stay is the foreign key of SSN of Patient.
The AssistingNurse of Undergoes is the foreign key of EmployeeID of Nurse.
The Physician of Undergoes is the foreign key of EmployeeID of Physician.
The Stay of Undergoes is the foreign key of StayID of Stay.
The Procedures of Undergoes is the foreign key of Code of Procedures.
The Patient of Undergoes is the foreign key of SSN of Patient.

##Role Access Policy (Column-Level):
Role: Nurse
Accessible Columns: Physician: EmployeeID, Name, Position; Patient: SSN, Name, Address, Phone; Nurse: EmployeeID, Name, Position, Registered; Appointment: AppointmentID, Patient, PrepNurse, Physician, Start, End, ExaminationRoom; Medication: Code, Name, Brand; Block: BlockFloor, BlockCode; Room: RoomNumber, RoomType, BlockFloor, BlockCode, Unavailable; On_Call: Nurse, BlockFloor, BlockCode, OnCallStart, OnCallEnd; Stay: StayID, Patient, Room, StayStart, StayEnd; Undergoes: Patient, Procedures, Stay, DateUndergoes, Physician, AssistingNurse

Based on the above schema and your role's column-level access policy, generate a SQL query to answer the question. If your role does not have access to the required columns, respond with: "Sorry, I cannot answer."


Question: What are the unique block codes that have available rooms?
Answer: SELECT DISTINCT blockcode FROM room WHERE unavailable  =  0
Permission: allowed (All required columns are permitted)
Gold SQL: SELECT DISTINCT blockcode FROM room WHERE unavailable  =  0