CREATE TABLE nurse (employeeid NUMBER, name CLOB, position CLOB, registered BOOLEAN, ssn NUMBER)
CREATE TABLE medication (code NUMBER, name CLOB, brand CLOB, description CLOB)
CREATE TABLE undergoes (patient NUMBER, procedures NUMBER, stay NUMBER, dateundergoes TIME, physician NUMBER, assistingnurse NUMBER)
CREATE TABLE procedures (code NUMBER, name CLOB, cost NUMBER)
CREATE TABLE appointment (appointmentid NUMBER, patient NUMBER, prepnurse NUMBER, physician NUMBER, start TIME, end TIME, examinationroom CLOB)
CREATE TABLE prescribes (physician NUMBER, patient NUMBER, medication NUMBER, date TIME, appointment NUMBER, dose CLOB)
CREATE TABLE trained_in (physician NUMBER, treatment NUMBER, certificationdate TIME, certificationexpires TIME)
CREATE TABLE department (departmentid NUMBER, name CLOB, head NUMBER)
CREATE TABLE patient (ssn NUMBER, name CLOB, address CLOB, phone CLOB, insuranceid NUMBER, pcp NUMBER)
CREATE TABLE room (roomnumber NUMBER, roomtype CLOB, blockfloor NUMBER, blockcode NUMBER, unavailable BOOLEAN)
CREATE TABLE on_call (nurse NUMBER, blockfloor NUMBER, blockcode NUMBER, oncallstart TIME, oncallend TIME)
CREATE TABLE physician (employeeid NUMBER, name CLOB, position CLOB, ssn NUMBER)
CREATE TABLE block (blockfloor NUMBER, blockcode NUMBER)
CREATE TABLE stay (stayid NUMBER, patient NUMBER, room NUMBER, staystart TIME, stayend TIME)
CREATE TABLE affiliated_with (physician NUMBER, department NUMBER, primaryaffiliation BOOLEAN)

Tell me the distinct block codes where some rooms are available.
SELECT DISTINCT blockcode FROM room WHERE unavailable = 0
SELECT DISTINCT "blockcode" FROM "room" WHERE "unavailable" = 0