How do I deal with concurrent changes in a web application?

Question

Here are two potential workflows I would like to perform in a web application.

Variation 1

• user sends request
• server reads data
• serve

Answer 1

If you do not have transactions in mysql, you can use the update command to ensure that the data is not corrupted.

UPDATE tableA  SET status=2  WHERE status = 1

If status is one, then only one process well get the result that a record was updated. In the code below, returns -1 if the update was NOT executed (if there were no rows to update).

PreparedStatement query;
query = connection.prepareStatement(s);
int rows = -1;
try
{
    rows = query.executeUpdate();
    query.close();
}
catch (Exception e)
{
   e.printStackTrace();
}
return rows;