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00:01 Hello and welcome to MongoDB for Python developers.
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00:04 Throughout this course, we're going to learn
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00:07 how to connect, model for and build applications with MongoDB,
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00:11 and we're going to do this with Python.
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00:14 We're going to look at the straightforward, lowest level way of doing things
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00:17 with PyMongo, and we're going to look at mapping classes
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00:20 through what's called an ODM, think orm for Mongo;
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00:24 an ODM to Mongo DB with Mongo Engine.
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00:28 And these come together to make a great combination.
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00:31 So let's begin by talking about document databases, how do they work?
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00:35 Well document databases in some ways
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00:38 are very much like standard relational databases,
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00:40 they have what you would think of as columns in that relational world,
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00:44 title, course id and duration in seconds here for example,
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00:48 but it also has nested data, so in a relational database
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00:51 we might have a lectures table that has
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00:54 some kind of foreign key constraint back to a chapter
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00:56 in this example we have on the screen here,
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00:59 but in fact in a relational database, we can embed those lectures
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01:02 inside of the chapter object, why is this good?
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01:06 Well, often, we spend so much time and energy
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01:09 building up an object hierarchy in our application
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01:12 and then tearing that apart into a bunch of little pieces
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01:15 what's called third normal form, basically normalizing our data
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01:18 in a relational database and then building a backup, taking it back apart
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01:22 and this object relational impedance mismatch
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01:25 makes it hard for us to reason about our code,
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01:28 it makes it a little bit less intuitive and so on.
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01:31 So with document databases, we can model our data
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01:34 the same way our application wants to use that data.
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01:37 We also have more flexibility in the schema,
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01:39 which means that deploying a new version of our application
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01:43 often does not require some kind of migration script and downtime,
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01:47 no, we just deploy the new version and the document database adapts to it.
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01:51 So document databases in my opinion are the best way to build applications,
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01:55 for the 80 percent case right, maybe you have some edge case
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01:58 where that doesn't make a lot of sense
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02:01 but most apps really benefit from using document databases.
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