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Hibernate Basics

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Introduction to Data Persistence

3:18 with Chris Ramacciotti

As a first stop on your way to Hibernate, you will first need to review a few basic concepts about relational databases.

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    To start on our path towards databases with Java, let's consider this scenario. 0:00
    You download a new contact manager app to your phone. 0:05
    And eager to use all its new sleek features, 0:08
    you start adding your friends and family's contact info. 0:11
    After adding a handful of people, 0:14
    you're interrupted by an important Facebook notification. 0:16
    Your mom just posted a throwback Thursday photo of you when you were nine years old, 0:19
    all decked out for trick or treating on Halloween. 0:23
    Mom, you like the photo then switch back to the contact manager app. 0:26
    A wave of anger overcomes you as you realize all your contacts are gone. 0:32
    With quick testing, you realize that every time you leave the app 0:37
    all the data you've entered disappears. 0:40
    What this app lacks is an acceptable answer to the following question. 0:44
    What good is an application whose underlying data is lost 0:48
    when the application unexpectedly goes down, is updated, or 0:51
    when a user logs out and log back in? 0:55
    What's clearly missing here is some sort of data storage mechanism. 0:58
    In software, this is referred to as data persistence. 1:03
    That is, data should live on or persist, after its application is powered down. 1:06
    This brings us to the most widely used form of data persistence. 1:13
    And that is the database. 1:16
    If you haven't already, you should check out our database courses, 1:19
    starting with SQL basics. 1:22
    I've linked to them in the teacher's notes. 1:23
    But, so that you have a general idea of the relational database concepts we'll 1:26
    be working with during this course, let's briefly touch on them here. 1:29
    Think of the relational database as a set of related spreadsheets 1:34
    where each of the spreadsheets is called a table. 1:38
    The tables themselves have columns which some people also call fields. 1:40
    In any given table, 1:46
    the columns refer to the pieces of information a table will hold. 1:47
    In the case of the contact manager, there might be a table of contacts, which could 1:51
    have five columns, an ID, first name, last name, email address and phone number. 1:56
    Being a table, it also has rows. 2:03
    These rows are the actual entries of data stored in the table. 2:05
    For the contacts table, each row contains the data for a single person. 2:09
    And even though we could store a hundred or even a thousand or 2:14
    more people in our contacts table, 2:17
    each row would still only consist of exactly five pieces of information. 2:19
    [SOUND] Let's take a quick look at that ID column. 2:24
    Typically, a database table has one column that uniquely identifies each row in 2:28
    the database, that is, no two rows can have the same ID. 2:33
    And even if a person's contact info is updated, 2:36
    the contact's ID will never change. 2:39
    This kind of column is called the primary key. 2:43
    And all of our tables will have a primary key column. 2:46
    Finally, a database almost always uses a specific language to 2:50
    interact with the underlying data. 2:54
    And that language is called structured query language, or SQL, for short. 2:56
    Think of this as the programmatic interface for databases. 3:01
    Like an API. 3:03
    That'll do for a database primer for our purposes in this course. 3:05
    Check the teachers notes for more on relational databases. 3:09
    Now, why don't you answer a couple questions before we start coding. 3:12
    I'll see you right back here. 3:16

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