Question: What are the transaction ids of those? | Here is the table of the transaction ids of transcation with an amount smaller than 3000. For example, they are  2, 4 , 5 | What are the transaction type codes of those?
SQL: SELECT T2.transaction_type_code FROM SALES AS T1 JOIN TRANSACTIONS AS T2 ON T1.sales_transaction_id   =   T2.transaction_id WHERE T2.amount_of_transaction  <  3000