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REALSQLDatabase (SQLite)
Triggers and Views
Issue: 5.2 (January/February 2007)
Article Description: No description available.
Article Length (in bytes): 4,212
Starting Page Number: 36
RBD Number: 5213
Resource File(s): None
Related Link(s): None
Known Limitations: None
Excerpt of article text...
For my last column on REALSQLDatabase/SQLite topics, we'll be covering transactions and a couple administration commands.
Transactions
A transaction is simply a group of database statements that will change the database in some way. You create a transaction when you want all these changes to be applied together or to not be applied at all, such as when there is a failure.
A typical example is a bank transfer. A bank transfer involves adding money to one account while removing it from another account. On the surface, that seems rather simple. This is what two SQL statements might look like to do this:
UPDATE account SET amount = amount - 1000 WHERE owner = 'Marc';
UPDATE account SET amount = amount + 1000 WHERE owner = 'Paul';
Now imagine what might happen to the accounts if there was a failure between decrementing Marc's account and incrementing Paul's account. If you were not using a transaction and instead just making the changes permanent after each command, then Marc's account would be out $1000, but no money would have been added to Paul's account. Obviously, that's bad!
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