Beginning SQL
Sean Collins

Lesson Plan
Theory
Relational Algebra & Sets
Practice
SQL
SQLite
Self-Directed Learning

Theory
Set Theory
The branch of mathematics that deals
with the formal properties of sets as
units (without regard to the nature of
their individual constituents) and the
expression of other branches of
mathematics in terms of sets

Examples
Union
Intersection
Set-Difference

Union

Intersection

Set-Difference

Why This Is Important
A whole branch of mathematics that deals
with collections of items and operations.
SQL is just one of many ways to describe
collections of items and operations.
Learning to think about data as discrete sets
of items opens new possibilities, because you
are given new operations to manipulate sets.

SQL
Structured Query Language
SQL is a language standard
Different databases products have extra
features tacked on to the language
Understand the structure of the language
Everything else is just syntax

SQLite
Free and Open Source relational database LIBRARY
Most SQL products are considered a “RDBMS”
Relational Database Management System
Which means they contain extra functionality
Networking
Backups
Authentication
Etc....

Things We Don’t Care
About. All We Want Is
SQL.

The SQL Data Model
Data in an SQL database
Tables
Columns
Rows

Tables
Tables are the “sets” of discourse in SQL
Tables contain data of the same type.
Customers in a Customer table
Orders in an Order table

Theory To Practice
Pull up all of our customers, and their
orders.
UNION
Pull up all of our customers who have ever
ordered something
INTERSECTION

Columns
Tables contain columns
Columns can have different data types
Dates
Timestamps
Integers
Currency

Digression: Keys
Most data has a unique identifier, somewhere
People: Social Security Numbers
Groceries: UPC/Barcodes
Cars: VIN
SQL has a data type to give hints to the
database engine about these unique identifiers

Keys
Typically a table will have a PRIMARY KEY
Often, it is a automatically incremented
integer
Blog post #1
Blog post #2
....

Connecting Tables
(Relations)
Two tables can be related through the use of
FOREIGN KEYS
Customer table has a primary key (customer_id)
Order table has a primary key (order_id) and a
column (customer) that references the customer
table.
The SQL database now knows about this relation.

Foreign Keys &
Referential Integrity
Foreign keys are used to enforce
REFERENTIAL INTEGRITY
You cannot have an order for a customer
that doesn’t exist.
You cannot delete a customer unless you also
delete their orders.

SQLite Example
We will now go through a hands-on exercise
with SQLite and the sample database from
GitHub
A more complete example database can be
found on the Chinook Project:
http://chinookdatabase.codeplex.com/
This is listed in Lesson_04.md of the GitHub
project