Doss the word "transaction" convey transfer of anything?
In economy does it mean any operation?
In databases does it mean any SQL command?
Where else is it used mostly except banks and databases?
Transaction is a word of Latinate origin with an abstract meaning that is readily adaptable to a variety of contexts. The verb transact means to carry out an action relating to the matter at hand, to conduct one's business, and so a transaction is something carried out, an action performed in the context of matters and business, with "business" understood very broadly. Almost any matter can be regarded abstractly, the actions relating to it seen as a transaction. Any communication. Any exchange, commercial or otherwise. The noun can also refer to the published record of such actions, as in the The Transactions of the Royal Society for the Advancement of Prepositions.
When the patient checks out of the dentist's office, they typically settle their account. During this transaction, the patient is asked whether they would like to schedule a check-up visit six months in the future.
An undercover narcotics agent will sometimes offer to sell some quantity of an illicit substance to a buyer. If the agent is found to have enticed a buyer who was not predisposed to the act, the transaction is considered entrapment.
Once partners are chosen and the pair enters into a sexual transaction, the act of mating is likely ... (The Last Ape: Pygmy Chimpanzee Behavior and Ecology, Takayoshi Kan, Evelyn Ono Vineberg. 1992)
When the database programmer moves money from one account into another, the debit and the credit must be treated as belonging to a single transaction; both steps in the process must be completed if the transaction is to be considered complete. If any step in a transaction cannot be accomplished for whatever reason, all steps of the transaction must be undone. The transaction is said to be "rolled back".
In a database transaction has a specific technical meaning, it's a unit of work that might comprise one or more SQL commands.
As an example consider a transfer of funds between two accounts. You write code with these meanings:
Begin Transaction Debit money from one account Credit money to other account Commit Transaction
The crucial point about the transaction is that either BOTH the credit and debit happen or, if some error occurs NEITHER happens; obviously it would be very bad if the debit happened and the credit didn't.
The important thing here is that only you the coder can know where the Begin and Commit need to go in order to do the correct business work. All sorts of clever stuff goes on in the database to deal with cases where failures happen in mid-transaction.