Show all main industry and total market value in each industry.
SELECT main_industry ,  sum(market_value) FROM company GROUP BY main_industry
SELECT main_industry ,  sum(market_value) FROM company GROUP BY main_industry
[{'Main_Industry': 'Banking', 'sum(market_value)': 580.4000000000001}, {'Main_Industry': 'Conglomerate', 'sum(market_value)': 415.9}, {'Main_Industry': 'Oil and gas', 'sum(market_value)': 1257.1000000000001}]