Show the transaction type code that occurs the most times.
select transaction_type_code from transactions group by transaction_type_code order by count(*) desc limit 1
Show the number of occurances of each transaction type code.
select transaction_type_code, count(*) from transactions group by transaction_type_code
Could you please order the transaction type codes by their number of occurances?
select transaction_type_code from transactions group by transaction_type_code order by count(*) asc
Show the first one.
select transaction_type_code from transactions group by transaction_type_code order by count(*) asc limit 1