Introduction
Simple DB is a database web service offered by Amazon.com. This
article will introduce the Simple DB service itself as well as the concepts
needed to work with it.
What is Cloud Computing?
Wikipedia defines Cloud Computing as “a style of computing
in which resources are provided as a service over the internet”. For me
personally, Cloud Computing means developing or managing a machine or service I
do not have physical responsibility for and is located somewhere in the
internet. I further break down Cloud Computing into two roles of activity,
either managing an entire virtual asset (virtual machine or application), or
just interacting with a specific service. Amazon Simple DB is the later
because we interact with the database through a service and are not responsible
for any operating system or database maintenance functions.
What is Simple DB
Amazon describes Simple DB as, “a web service providing the core
database functions of data indexing and querying”. The product is designed so
that neither IS or the developer needs to manage, maintain, or administrate the
database server or the operating system underneath.
Simple DB is one of several services collectively known as
Amazon Web Services (AWS). All the AWS products are Cloud (internet) based.
Other Amazon Web Service products include file storage (Simple Storage
Service), message queuing (Simple Queue), and computing capacity (virtual
machines called Elastic Compute Cloud).
Simple DB Pricing
Because Simple DB is an internet service, there is no
equipment to purchase. Pricing is based on the amount of data stored and the
amount of data transferred from the service to your consuming application.
Pricing details can be found on Amazons web site at the following URL: http://aws.amazon.com/simpledb/#pricing
.
Domains
The database model is non-relational. Within the database,
you create Domains, these are similar to traditional database Tables. One
difference though, because the model is non-relational, there is no command to
JOIN (INNER JOIN or OUTER JOIN for example) one Domain to another and produce a
result set. It was easiest for me to consider a Domain layout in the same way
a highly non-normalized table used in reporting may be laid out. For example,
in a typical relational database application for processing Sales, we would create
a Customer Table, a Products Table, and a Sales Table. All would be related to
each other using Keys as shown below:
But for the reporting side of Sales, we may create a
non-normalized Table with just the subsets of information all contained in one
Table.
The layout of this “SalesReporting” table would produce very
quick query results for reports. The same type of demoralization is required
when working with Simple DB.
Each Customer Account you have (think of a Customer Account
as a Database) can contain 100 Domains. Each Domain can store up to 10
Gigabyte of data.
Items, Attributes, and Values
A Simple DB Item is a row of data inside a Domain. Columns
of the Domain are called Attributes.
There can be up to 256 Attributes (Columns) per Domain
(Table).
Values are the actual data stored in the Domain. The max
length of a Value is 1024 bytes.
Attributes (Columns) can contain multiple Values (data).
For example, imagine we have a used car lot with six cars, two different models
each coming in three colors. In a regular database, we would usually create
six rows of data, one row of data for each individual car as shown below:
With Simple DB however, inserting multiple values into an
Attribute is allowed and encouraged. We could store our color attribute values
together for each model of car. Now only two rows (Items) of data would be
required.
There are special commands used to retrieve and work with
these multivalue Items.
Data Types
There is only one Data Type with Simple DB, String. All
Values (data) in Simple DB are stored as UTF-8 Strings. Because all stored
data is a String, care must be taken when an Attribute (column) is used in a
WHERE or ORDER BY type SELECT statement. For example, Dates should be entered
in the format of YYYY-MM-DD (ISO 8601). Doing this will produce proper
lexicographical comparisons. Numbers also need special handling if they are to
be sorted or range selected. A process called Zero Padding is used for this.
To Zero Pad, add zeros to the front of each number until all are the same
length. For example if you had two numbers, 12 and 6, pad the 6 to become 06.
Now on a sort, the six will list before 12 as we would expect in Ascending
order. Your application will have to trim the leading zeros. Next month, we’ll
explore this topic in full, including working with negative numbers.
Interface
Currently there isn’t any Management Console for Simple DB.
All tasks, including Creating Domains, entering data, data definition tasks,
and all data manipulation tasks are done via a programming interface you
create. Multiple languages are supported including Java, C#, Pearl, PHP, VBNet.
The following examples will be done in Visual Studio Dot Net with c#. To
begin, download the Visual Studio sample from the AWS web site.
This first example creates a new Domain (Table).
Two using statements will be needed to reference Simple DB:
using Amazon.SimpleDB;
using Amazon.SimpleDB.Model;
Next, anytime we interact with Simple DB, an Access Key and
private Secret key are passed.
String accessKeyId = “myAccessKey”;
String secretAccessKey = “mySecretKey”;
Now a new instance of Simple DB is invoked using our keys.
AmazonSimpleDB service = new AmazonSimpleDBClient(accessKeyId, secretAccessKey);
Lastly, a new Domain (Table) is created with the name “MyStore”.
CreateDomainRequest request = new CreateDomainRequest().WithDomainName(“MyStore”);CreateDomainSample.InvokeCreateDomain(service, request);
When the application is run from Visual Studio, a command
box will confirm the Domain was created.
The “BoxUsage” can be used to figure out the actual cost
that will be charged for running this statement.
Conclusion
The Amazon Simple DB is a web database service offered by
Amazon. If you are a regular Oracle or SQL Server professional, a couple of
Simple DB rules will need to be remembered, such as when working with Dates and
Numbers and the fact that Simple DB is not relational. Next month, we’ll
create sample APSX web applications that will fully explore the Simple DB
syntax.
