The following case can describe this problem.

Database transaction concurrency problem: there are five kinds of problems: dirty read, non-repeatable read, phantom read, the first kind of lost update, the second kind of lost update.
In order to solve the above problems, we proposed the concept of isolation level. Different isolation levels can deal with different concurrency and syncronized problems.we can using different isolation levels can prevent the expected concurrency problems.

Meanwhile,regard to this problem,we can lock the database,making sure that only one person allowed to operate the database at a time.Other people should waiting for the previous operation,but this way is low efficiency.A better method is to let user operate on a copy of the temporary database,when the user submit the whole manipulation to the data base ,the database manage system will handle with all the operation in a proper order,and manipulate on the true database eventually.