Show the average transaction amount for different transaction types.
SELECT transaction_type_code ,  avg(amount_of_transaction) FROM TRANSACTIONS GROUP BY transaction_type_code
SELECT transaction_type_code ,  avg(amount_of_transaction) FROM TRANSACTIONS GROUP BY transaction_type_code
[{'transaction_type_code': 'PUR', 'avg(amount_of_transaction)': 25945880.3716125}, {'transaction_type_code': 'SALE', 'avg(amount_of_transaction)': 11198167.237771427}]