Presentation that I gave as a guest lecture for a summer intensive development course at nod coworking in Dallas, TX. The presentation targets beginning web developers with little, to no experience in databases, SQL, or PostgreSQL. I cover the creation of a database, creating records, reading/querying records, updating records, destroying records, joining tables, and a brief introduction to transactions.

1. Introduction to
PostgreSQL
Joel Brewer
@jahbrewski
brewerdigital.com

2. • Introduction to databases
• Introduction to PostgreSQL
• CRUD
• Create
• Read/query
• Update
• Destroy
• Joins
Overview

3. What’s a database?
• A database stores data!
• It is a collection of information that is organized so
that it can be easily accessed, managed, and
updated

4. Why do I care?
• If you’re building a web application, you’re going to
have data to store
• What data do these websites store?
• Facebook (users, profiles, groups, events,
businesses)
• Twitter (users, tweets)
• CNN (articles, comments)

5. What’s PostgreSQL?
• PostgreSQL (“post-gress-Q-L”) is an open source
object-relational database system
• Open source = free!
• Object - some object-oriented paradigms are
natively supported, such as objects, classes, and
inheritance
• Relational - database is structured to recognize
relations among stored items of information

6. Let’s make a database
$ createdb testdb
$ psql testdb
=> SELECT version();
Note: to exit psql just type “q”

7. Let’s make a table
=> CREATE TABLE spaceship (
nickname varchar(35),
crew_size int,
commission_date date
);

8. CRUD
• CRUD (create, read, update, delete) are the four
basic functions you perform on a database

9. Create
• Examples:
• Creating a new account on Facebook
• Posting a picture on Instagram
• Creating a new tweet on Twitter

10. Read
• Examples:
• Browsing your Facebook timeline
• Looking at pictures on Instagram
• Reading the latest article on CNN

11. Update
• Examples:
• Changing your password
• Editing a comment
• Changing your relationship status on Facebook

12. Destroy
• Examples:
• Deleting a picture on Facebook (well, maybe…)
• Deleting a tweet on Twitter
• Unfriending somebody on Facebook

13. Create
• SQL uses the INSERT statement to create a new
row
=> INSERT INTO spaceship VALUES (‘falcon’, 15,
‘2040-04-16’);
• Add a few more records to your spaceship table
Note: you must enter values in the same order you used
during creation of the table

14. Read
• To read data from your database, one or more
tables must be queried
• The SELECT statement is used to perform queries
=> SELECT * FROM spaceship;

15. Read
• The * is a shorthand for “all columns”
• The same result could be achieved with:
=> SELECT nickname, crew_size, commission_date
FROM spaceship;

16. Read
• Queries can be ordered by adding ORDER BY
[column] to the end of your query
=> SELECT * FROM spaceship ORDER BY
nickname;
=> SELECT * FROM spaceship ORDER BY
commission_date;

17. Read
• Queries can be “qualified” by adding a WHERE
clause that specifies which rows are wanted
=> SELECT * FROM spaceship WHERE
commission_date > ‘2030-04-16’;
=> SELECT * FROM spaceship WHERE nickname =
‘falcon’;
=> SELECT * FROM spaceship WHERE crew_size >
5;

18. Update
• Rows can be updated using the UPDATE
command
• Update row(s) matching WHERE clause
=> UPDATE spaceship SET nickname = ‘eagle’
WHERE nickname = ‘falcon’;
• Careful, default updates all rows!
=> UPDATE spaceship SET crew_size = 20;

19. Destroy
• Rows can be destroyed using the DELETE
command
• Delete row(s) matching WHERE clause
=> DELETE from spaceship WHERE nickname =
‘falcon’;
• Careful, default deletes all rows!
=> DELETE from spaceship;

20. Congratulations!
• Now you know how to CRUD a PostgreSQL
database!

21. Digging Deeper…
• Joins between tables
• Transactions

22. But First…
• Install sample database that we can run some
joins/queries on
• https://code.google.com/p/northwindextended/down
loads/detail?name=northwind.postgre.sql

23. But First…
$ createdb northwind
$ psql northwind < northwind.postgre.sql
$ psql northwind

24. But First…
• Lets do a little exploration:
=> dt
=> d+ orders
=> d+ customers

25. Joins - Inner Join
• SQL inner join is the most common type of join
• Used to combine rows from two or more tables,
based on a common field between them

26. Joins - Inner Join
• Which company placed each order?
• Return the OrderID, CustomerID, and
CompanyName for each order
• Using an Inner Join we can join the orders table
with the customers table, using the CustomerID
=> SELECT “OrderID”, orders.”CustomerID’, “CompanyName”
FROM orders
INNER JOIN customers
ON orders.”CustomerID”=customers.”CustomerID”;

27. Joins - Inner Join
• What products were ordered, and what were their
prices?
• Return the ProductID, UnitPrice, and ProductName for
each item of a given order
• Using an Inner Join we can join the order_details table
with the products table
=> SELECT order_details.”ProductID”, ”UnitPrice”, “ProductName”
FROM order_details
INNER JOIN products
ON order_details.”ProductID”=products.”ProductID”
WHERE “OrderID” = 10248;

28. Joins - Left Outer Join
• The LEFT OUTER JOIN keyword returns all rows
from the left table (table1), with the matching rows
in the right table (table2). The result is NULL in the
right side when there is no match.

29. Joins - Left Outer Join
• “Let me see a list of all of our customers, and any
orders they have made”
• Need to return the CompanyName and associated
OrderID (if any)
• Using a Left Outer Join we can join the orders table
with the customers table
=> SELECT customers."CompanyName", orders.”OrderID"
FROM customers
LEFT OUTER JOIN orders
ON customers."CustomerID"=orders."CustomerID"
ORDER BY customers."CompanyName";

30. Joins - Right Outer Join
• The RIGHT JOIN keyword returns all rows from the
right table (table2), with the matching rows in the
left table (table1). The result is NULL in the left side
when there is no match.

31. Joins - Full Outer Join
• The FULL OUTER JOIN keyword returns all rows
from the left table (table1) and from the right table
(table2).The FULL OUTER JOIN keyword
combines the result of both LEFT and RIGHT joins.

32. Transactions
• “A transaction is a unit of work that is performed against a database.
Transactions are units or sequences of work accomplished in a logical
order, whether in a manual fashion by a user or automatically by some
sort of a database program.”
• “You use transactions when the set of database operations you are
making needs to be atomic. That is - they all need to succeed or fail.
Nothing in between.” http://stackoverflow.com/questions/9317866/when-to-use-transactions-in-sql-server
• Examples:
• Money transfer
• Order fulfillment
• Can you think of any others?

33. Joel Brewer
@jahbrewski
brewerdigital.com
joel@brewerdigital.com