Handling the concurrent request while persisting in oracle database?

Question

I have this scenario ,on a airline website (using Java) two separate customers send two requests at same time to book a same seat in same airline
from New York to Chica

Answer 1

Aside from doing everything in a single UPDATE by carefully crafting WHERE clause, you can do this:

Transaction 1:

• SELECT ... FOR UPDATE exclusively locks the row for the duration of the transaction.
• Check if the returned status of the row is "booked" and exit (or retry another row) if it is.
• UPDATE the row and set its "status" to "booked" - it is guaranteed nobody else updated it in the meantime.
• Commit. This removes the exclusive lock.

Transaction 2:

• SELECT ... FOR UPDATE blocks until Transaction 1 finishes, then exclusively locks the row.
• The returned status of the row is "booked" (since Transaction 1 marked it that way), so exit (or possibly retry another row).