CREATE TABLE furniture (furniture_id NUMBER, name CLOB, num_of_component NUMBER, market_rate NUMBER)
CREATE TABLE furniture_manufacte (manufacturer_id NUMBER, furniture_id NUMBER, price_in_dollar NUMBER)
CREATE TABLE manufacturer (manufacturer_id NUMBER, open_year NUMBER, name CLOB, num_of_factories NUMBER, num_of_shops NUMBER)

find the total market rate of the furnitures that have the top 2 market shares.
SELECT SUM(market_rate) FROM furniture ORDER BY market_rate DESC LIMIT 2
SELECT SUM("market_rate") FROM "furniture" ORDER BY "market_rate" DESC FETCH FIRST 2 ROWS ONLY