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It's hard to imagine a database that would stay totally static and never change.
Our SQLite3-Ruby gem obliged and gave us an array that contains one array that contains one element––the last inserted row ID. So, let's put it all together with our new-and-improved on an object that has already been persisted and has an analogous database row?
It would have the effect of creating a new database row with the same attributes as an existing row.
For example, a customer who uses your online market place updates their billing information or makes a new purchase.
A user of your social networking site "friends" another user, creating a new association between them.
If it does, then only one of the join rows will be used to update the target row, but which one will be used is not readily predictable.
Because of this indeterminacy, referencing other tables only within sub-selects is safer, though often harder to read and slower than using a join.
What do we need to do in order to successfully update a record? Then, we make some changes to it, and finally, save it once again.
In our Ruby ORM, where attributes of given Ruby objects are stored as an individual row in a database table, we will need to retrieve these attributes, reconstitute them into a Ruby object, make changes to that object using Ruby methods, and save those (newly updated) attributes back into the database. For the purposes of this example, we'll be working with a fictitious music management app that allows the user to store their songs.
You could even commit a major faux pas by trying to contact someone who has died.