Defining transactions
In the previous chapters, we mentioned that we should try and write all the database changes with a single declarative statement. However, when it comes to reality, there comes a time when you cannot write everything to a database using one single SQL statement. This doesn't mean it will be just one single SQL statement; there might be multiple statements that will update the database correctly. If, by chance, any problem is encountered in the statement or a group of statements, then none of the database changes should be written. In other words, you will require the SQL statements to work as an individual unit and execute tasks sequentially in a way that allows the changes to be reversed and hides uncommitted changes from other processes. In this case, either all of the statements should be executing successfully or none of them should be executing.
A real-world example can be taken from the banking domain, where all transactions are recorded in debit and credit...