CREATE TABLE staff (staff_id NUMBER, gender CLOB, first_name CLOB, last_name CLOB, email_address CLOB, phone_number CLOB)
CREATE TABLE customers (customer_id NUMBER, customer_type_code CLOB, address_line_1 CLOB, address_line_2 CLOB, town_city CLOB, state CLOB, email_address CLOB, phone_number CLOB)
CREATE TABLE complaints (complaint_id NUMBER, product_id NUMBER, customer_id NUMBER, complaint_outcome_code CLOB, complaint_status_code CLOB, complaint_type_code CLOB, date_complaint_raised TIME, date_complaint_closed TIME, staff_id NUMBER)
CREATE TABLE products (product_id NUMBER, parent_product_id NUMBER, product_category_code CLOB, date_product_first_available TIME, date_product_discontinued TIME, product_name CLOB, product_description CLOB, product_price NUMBER)

Count the number of different complaint type codes.
SELECT COUNT(DISTINCT complaint_type_code) FROM complaints
SELECT COUNT(DISTINCT "complaint_type_code") FROM "complaints"