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- [Instructor] For our
first series of examples

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in this lesson, we'll be
focusing on relational databases

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and the structured query language.

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So as you probably know
a database is simply

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a collection of data and
traditional relational database

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management systems focus on
storing that data in tables

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and sometimes many tables

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that have relationships between them.

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We'll be focusing on using
the Structured Query Language

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or sequel as many people referred to it

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some read it by the letters SQL

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and that is the pretty
much universal language

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of relational database systems.

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We'll demonstrate some
queries that extract data

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from a database and we'll also
take a look at capabilities

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for inserting records into a database,

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updating records and
deleting records as well.

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Now for the purpose of these
examples we'll be focused

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on using the sequel light
database management system,

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which comes bundled with Python,

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and as you'll see there's
also a module built

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into the Python standard library

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for interacting with sequel light.

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Now when we're working
with relational data,

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we're going to be using
tables that consist

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of rows and columns,

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and the relational database itself is just

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a table based representation of data.

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So this is a simple employee table

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in which we have several rows of data,

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several columns of data,

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and specifically you notice that we marked

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the number column as a primary key.

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This is a value that
helps uniquely identify

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each of the rows within a given table.

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Now every row describes one unique entity

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in the case of our employee
table up above one employee

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and the columns within a given row

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are the individual pieces
of data or attributes

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associated with that unique entity,

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and as I mentioned the primary key,

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is usually a column but it
could also be a group of columns

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and that is used to uniquely
identify every one of the rows.

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Now when you're working with those tables,

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one of the most common things you'll do

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is use sequel queries to grab subsets

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of the data in a given table.

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So this is a result of an example

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in which you select from
that employee table,

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each department and its location,

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and here we happen to
be presenting the data

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in increasing order by department number.

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So one of the things that we'll
be able to do for example,

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is to sort the results
that we are getting back

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when we query the database.

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Now as we work our way
through this section 16_02

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and its subsections, again
we'll be focused on using

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the sequel light database
management system.

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It's an open source DBMS, and
again included with Python,

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most of the popular
database systems out there

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have Python support, so once you choose

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whichever database management
system you want to use,

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you would simply take
advantage of whatever

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Python module they provide

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for interacting with that database.