HTML 5 Web SQL Database Transaction commit or rollback when refreshing page

1. The transaction will be committed.
2. Yes, to rollback explicitly, you must invoke invalid query explicitly. This is recommended workaround since the quick-and-dirty API is missing abort method.

Regarding AJAX, be ready all data, before you start a write transaction. You won't have any problem as you described. Use database constraint (UNIQUE, FOREIGNKEY) as much possible.

Have you found a way to do AJAX calls during the transaction? I haven't finished reading the whole spec, but so far it looks like once your SQLTransactionCallback or SQLTransactionSyncCallback returns, you can’t add any more stuff to the transaction — or can you? Maybe from the results callback?

Edit:Now that I look again, the spec (which contains many fewer errors than the Apple document you linked to, but is not as easy to read) says this:

1. If the method [executeSql] was not invoked during the execution of a SQLTransactionCallback, SQLStatementCallback, or SQLStatementErrorCallback then raise an INVALID_STATE_ERR exception.

So I think that means there's no way to do it.

Further edit: No, wait! As long as the SQLStatementCallback takes some time to get called, you could busy-wait doing select 3 + 4 over and over again, each time from the statement callback of the previous select 3 + 4, until your AJAX call sets a flag somewhere that has the data you want. This is terrible programming (it'll eat lots of CPU for no good reason, might block lower-priority tasks like redisplaying the page) but I think it's probably the only way to keep a transaction open for an arbitrary period of time. Too bad you can't select 3 + 4, sleep(1) in SQLite.

In general SQLite (the underlying storage engine here) rolls back uncompleted transactions. I haven’t yet tested the page-reload error case you're asking about. I would be very surprised if it was committed.

By the way, thank you very much for posting this question. I had been trying to figure out how to get the transaction to rollback, even though it is meticulously documented in the original spec.