Update process

Question

Hello all,
I've created a set of classes that represent rows in my database. I've defined several instance variables that associate to the columns in my table (a simple example is provided below).
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class TableRow
String username, password, emailAddress;
Date createDateTime, modifyDateTime;
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When a user updates the instance variables (using the methods I've defined in the class), I'd also like to update the records in my database.
In order for me to select the row to update in my database table, I need to reference the rows original values. However, because the change to the instance variables have already been performed, I only have the new values available to me.
Should I create another set of instance variables that will hold my original values, then use them to select the records to update? Or is an updatable resultset what I need to use here?
Creating another set of variables to hold my original values seems inefficient, but its how I've managed it with structured programs. Please advise.
R. Alcazar

Answer 1

You said:
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class TableRow
String username, password, emailAddress;
Date createDateTime, modifyDateTime;
================================hartmut said:
If you have a clean DB schema, each table has a unique
key column. So you have to save the keys only.Suggestion: Your db schema should have a primary key int in each table. Your class should have an int data member called "ID", and a boolean called "changed", along with set() and get() methods for each. Whenever the set methods are called, "changed" is set to true. When you save data, updates are only necessary when "changed" is true, and the sql can be done by using getID() to indetify the row to be updated. So unless you need to know that, for example, emailAddress changed and password did not, you can just include all columns of the table in the update statment.
Also, you can factor the ID and changed logic out into a base class. I call mine PersistentEntity, and all classes that have their data stored in a db extend that class.