Practical 1 – Introduction to PostgreSQL
Learning Outcomes
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Understand what PostgreSQL is.
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Able to connect to PostgreSQL database server from a client application such as pgAdmin.
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Able to load a sample database into the PostgreSQL database server.
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Able to perform simple queries in PostgreSQL
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SELECT, ORDER BY, WHERE, DISTINCT, IN, BETWEEN, LIKE, LIMIT
Part 1 : What is PostgreSQL?
PostgreSQL is a general purpose and object-relational database management system. PostgreSQL is free
and open source software. It allows you to add custom functions developed using different programming
languages such as C/C++, Java, etc. In PostgreSQL, you can define your own data types. Some featured
companies who have built products and solutions using PostgreSQL are Apple, Fujitsu, Red Hat, Cisco,
Juniper Network, etc.
Part 2 : Connect to database using client pgAdmin
Here, we will connect to PostgreSQL database server using pgAdmin GUI application. By using pgAdmin
GUI application, you can interact with PostgreSQL database server via an intuitive user interface.
The following illustrates how to connect to a database using pgAdmin:
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First, launch the pgAdmin application.
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Second, double-click the PostgreSQL 9.2 under the Servers item. pgAdmin will ask you for the
password. Enter the password for the postgres user (password is postgres). Click OK button to log in
to the PostgreSQL server.
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Third, choose the postgres database and click Execute Arbitrary SQL queries tool from the
pgAdmin’s toolbar.
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Fourth, enter the following statement:
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Fifth, click the execute query button in the toolbar, pgAdmin will display the result in the output panel.
Part 3 : Load a sample database – the DVD rental database
The DVD rental database represents business processes of a DVD rental store. The DVD rental database
has many objects including: 15 tables, 7 views, 8 functions, 1 domain, and 1 trigger. The 15 tables are as
follows:
Table name
Brief description
actor
stores actors data including first name and last name.
film
stores films data such as title, release year, length, rating, etc.
film_actor
stores the relationships between films and actors.
category
stores film’s categories data.
film_category
stores the relationships between films and categories.
store
contains the stores data including manager staff and address.
inventory
stores inventory data.
rental
stores rental data.
payment
stores customer’s payments.
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staff
stores staff data.
customer
stores customers data.
address
stores address data for staff and customers.
city
stores the city names.
country
stores the country names.
The relational database schema for the DVD Rental database is shown below.
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Download the DVD Rental sample database from the LCMS page. The database file is in zipformat
(dvdrental.zip) so you need to extract it to dvdrental.tar.
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In pgAdmin, right mouse click on the Databases and click the new Database.. menu item to create a
new database.
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Enter a name for the database and click the OK button.
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Right mouse click on the dvdrental and choose the Restore… menu item.
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Provide the path to database file and click the Restore button
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Wait for few seconds and click the Done button when the pgAdmin completes restoring the
database.
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Verify the loaded sample database
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Open the dvdrental database from object browser panel, you will see the tables in the schema and
other database objects as the following picture:
Part 4 : Explore server and database objects
PostgreSQL provides many server and database objects. In order to leverage the features of each object
that PostgreSQL provides effectively, it is important to understand what each object is and how to use it
effectively.
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Server service
When you install a PostgreSQL instance, you will have
a corresponding PostgreSQL server service. It is also
known as PostgreSQL server. You can install multiple
PostgreSQL servers on a physical server using different
ports and having different locations to store data.
Database
A database is a container of other objects such as
tables, views, functions, indexes, etc. You can create as
many databases as you want inside a PostgreSQL
server.
Table
The table is used to store the data. You can have many tables
in a database. A special feature of PostgreSQL table is
inheritance. Meanings a table (child table) can inherit from
another table (parent table) so when you query data from the
child table, the data from parent table is also showing up.
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Schema
A schema is a logical container of tables and other objects
inside a database. Each PostgreSQL database may have
multiple schemas. It is important to note that schema is a
part of ANSI-SQL standard.
Tablespace
A tablespace is where PostgreSQL stores the data.
PostgreSQL tablespace enables you to move your data to
different physical location across drivers easily by using
simple commands. By default, PostgreSQL provides two
tablespaces: pg_defaultfor storing user’s data and
pg_globalfor storing system data.
View
The view is a virtual table that is used to simplify complex
queries and to apply security for a set of records.
PostgreSQL also provides you with updatable views.
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Function
The function is a block reusable SQL code that returns a
scalar value of a list of records. In PostgreSQL, functions
can also return composite objects.
Operator
The operator is a symbolic function. PostgreSQL allows you to define custom operators.
Cast
Casts enable you to convert one data type into another data type. Casts actually backed by functions to
perform the conversion. You can also create your own casts to override the default casting provided by
PostgreSQL.
Sequence
Sequences are used to manage auto-increment columns
that defined in a table as a serial column.
Extension
PostgreSQL introduced extension concept since version 9.1
to wrap other objects including types, casts, indexes,
functions, etc into a single unit. The purpose of extensions
is to make it easier to maintain.
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Part 5 : Write and execute SQL queries
1. List names of all staff.
2. List names of all customers ordered by their last name. If two customers have the same last
name, then the records are ordered by their first name.
3. List names of all customers whose last name starts with “Moo”.
4. List titles of all films whose description contains the word “panorama”.
5. List the different film categories.
6. List details of films whose length is less than 60 minutes.
7. List details of films whose length is between 60 and 120 minutes.
8. Give the number of films.
9. Give the number of japanese films.
10. List the title and release year of films starred actor Reese West.
11. List the title of films in the following four categories: Comedy, Action, Horror, Children
12. List the total amount paid by customer Douglas Graf.
Source http://www.postgresqltutorial.com/
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