Show the average share count of all investors.
select avg(share_count) from transactions
Count the number of investors who make any transaction with share count greater than 100.
select count(*) from investors as t1 join transactions as t2 on t1.investor_id = t2.investor_id where t2.share_count > 100
Show their details.
select t1.investor_details from investors as t1 join transactions as t2 on t1.investor_id = t2.investor_id where t2.share_count > 100