Introduction to PostgreSQL

Introduction to Databases with PostgreSQL
Gabrielle Roth
PDXPUG & FreeGeek
Nov 9, 2010

Outline
Intro to Databases (discussion)
PostgreSQL (discussion)
psql (hands-on)
SQL (hands-on)
...break somewhere in here, 7:30...
Practice db + more SQL (hands-on)
Basic Admin + GUI Tools (discussion)
Questions
Gabrielle Roth (PDXPUG & FreeGeek) Introduction to Databases with PostgreSQL Nov 9, 2010 2 / 1

Introductions
__ __
/ ~~~/ . o O ( Hi! )
,----( oo )
/ __ __/
/| ( |(
^ /___ / |
|__| |__|-"
Thanks to Hayley J Wakenshaw for the Elephant

Databases!
A place to keep your data!

Relational databases
Based on Relational Calculus
Data is stored in ”relations”
”Normalized”

PostgreSQL
- How do you say that?
- It’s the database *server*
- We think it’s the best.

Get connected.
chmod 600 /path/to/id_pdxpug
ssh -i /path/to/id_pdxpug pdxpug@207.173.203.228

Pg command-line interface
- psql
- - -help
- psql -U [username] -d pdxpug
- h
- ?
- other useful commands

SQL
- Declarative programming language
- ...let’s do ”Hello World”.

Hello, World.
SELECT ’Hello, World.’;
...oh yeah, and there’s command-completion, too.

CREATE TABLE
CREATE TABLE animals
(name varchar(32) primary key,
skin varchar(32),
legs int);

INSERT
INSERT INTO animals
VALUES (’cat’, ’fur’, ’4’);

multi-valued INSERT
insert into animals
values
(’dog’, ’fur’, ’4’),
(’bird’, ’feathers’, ’2’),
(’snake’, ’scales’, ’0’);

SELECT
SELECT * FROM animals;
SELECT name, legs FROM animals;
SELECT * FROM animals
ORDER BY name;
SELECT count(*) FROM animals;
SELECT SUM(legs) FROM animals;

UPDATE
UPDATE animals
SET name = ’kitty’ WHERE name = ’cat’;

Transactions
BEGIN;
...your stuff...
...check your stuff with a SELECT...
ROLLBACK or COMMIT as desired

DELETE
BEGIN;
DELETE FROM animals WHERE legs=2;
[ROLLBACK or COMMIT]

Exercises
- add an animal of your choice
- update its name
- delete all animals with four legs

MOAR TABLEZ
www.postgresqlguide.com/postgresql-sample-database.aspx

ERDs
- Entity-Relationship Diagrams
- Graphical representation of the relations
- ...and how they’re connected (JOINed)

The time has come, the walrus said, to talk of many things.

Load ’er up!
i /home/pdxpug/create_tables.sql
i /home/pdxpug/populate_tables.sql

Working with the sample db
- d
- what are these seq relations?
- d item
- s
- e

DISTINCT
SELECT fname, lname FROM customer
SELECT count(lname) FROM customer;
SELECT DISTINCT lname FROM customer;
SELECT count(DISTINCT(lname)) FROM customer;

- PRIMARY vs FOREIGN keys
- Natural vs Surrogate keys
- JOINs
- pset null ’[null]’

JOINs
SELECT * FROM item;
SELECT * FROM stock;
SELECT i.description, i.cost_price, i.sell_price, s.quantity
FROM item i
JOIN stock s ON i.item_id = s.item_id;
FROM item i
LEFT JOIN stock s ON i.item_id = s.item_id;
FROM item i
RIGHT JOIN stock s ON i.item_id = s.item_id;Gabrielle Roth (PDXPUG & FreeGeek) Introduction to Databases with PostgreSQL Nov 9, 2010 26 / 1

...and the dreaded Cartesian JOIN
SELECT * FROM item;
SELECT * FROM stock;
FROM item i, stock s;
FROM item i
CROSS JOIN stock s;

VIEWs and TEMP TABLEs
CREATE VIEW my_view AS SELECT field FROM table;
vs.
CREATE TEMP TABLE my_temp_table AS SELECT field FROM table;

VIEWs and TEMP TABLEs
CREATE VIEW view_in_stock AS
SELECT i.item_id, i.description, s.quantity
FROM item i
LEFT JOIN stock s ON i.item_id=s.item_id;
SELECT * FROM view_in_stock;
try:
pset null ’0’

subSELECTs
SELECT date_placed FROM orderinfo
WHERE customer_id IN
(SELECT customer_id FROM customer
WHERE lname = ’Matthew’);
SELECT date_placed FROM orderinfo
WHERE customer_id IN
(SELECT customer_id FROM customer
WHERE (fname, lname) = (’Alex’,’Matthew’));

Exercises
1 How many items are currently in stock?
2 In which towns do we have customers?
3 Experiment with RIGHT JOIN with the original sample queries.
4 What are the barcodes for each item?
5 What is the name + total ”our cost” value of each item currently in stock?
6 What is the name + total ”selling cost” value of each item currently in stock?
7 What are the total ”our cost” and ”sell cost” values of all items in stock?
8 How much was shipping on each order?
9 What items were ordered by people with the last name ”Stones”?
10 How much was the total shipping per person?

Basic Admin
- initdb
- PGDATA
- postgresql.conf
- pg hba.conf
- stop/start/restart/reload

Basic Admin
- SELECT version();
- CREATE ROLE
- backups and upgrades
- pg dump, pg dumpall, pg upgrade
- logs

GUI Tools
- pHpPgAdmin
- pgAdminIII

Extras
- Natural keys vs Surrogate keys
- indexes
GRANT USAGE ON SCHEMA [schema] TO [otheruser];
GRANT SELECT ON [table] TO [otheruser];

Book giveaway!
SELECT (random() * 100);

Where to get help
- www.postgresql.org/community/lists/
- #postgresql
- PDXPUG

Reading List
www.postgresql.org/docs
Manga Guide to Databases Takahashi, Mana
Database Design for Mere Mortals Hernandez, Michael J
SQL for Smarties Celko, Joe
Introduction to Database Systems Date, CJ
Relational Model for Database Management Codd, EF

__ __
/ ~~~/ . o O ( Thank you! )
,----( oo )
/ __ __/
/| ( |(
^ /___ / |
|__| |__|-"

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