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Exposure to Computer Disciplines

Notes In a future post, I’ll describe an approach I’ve used for database versioning that has worked well
for many years of commercial development.

Prepare database for school management using students and applications
received.

8.4 Database at Work

Databases have been a staple of business computing from the very beginning of the digital era.
In fact, the relational database was born in 1970. Since then, relational databases have grown in
popularity to become the standard. Originally, databases were flat. This means that the information
was stored in one long text file, called a tab delimited file. Each entry in the tab delimited file is
separated by a special character, such as a vertical bar (|). Each entry contains multiple pieces of
information (fields) about a particular object or person grouped together as a record. The text file
makes it difficult to search for specific information or to create reports that include only certain
fields from each record.
You can see that you have to search sequentially through the entire file to gather related information,
such as age or salary. A relational database allows you to easily find specific information. It also
allows you to sort based on any field and generate reports that contain only certain fields from
each record. Relational databases use tables to store information.
In the relational database example, you can quickly compare salaries and ages because of the
arrangement of data in columns. The relational database model takes advantage of this uniformity
to build completely new tables out of required information from existing tables. In other words,
it uses the relationship of similar data to increase the speed and versatility of the database.

The “relational” part of the name comes into play because of mathematical relations. A typical
relational database has anywhere from 10 to more than 1,000 tables. Each table contains a column
or columns that other tables can key on to gather information from that table. Look at the table
below that matches the number in the City column of the above table with the name of a city.
By storing this information in another table, the database can create a single small table with the
locations that can then be used for a variety of purposes by other tables in the database. A typical
large database, like the one a big Web site, such as Amazon would have, will contain hundreds
or thousands of tables like this all used together to quickly find the exact information needed at
any given time.
Relational databases are created using a special computer language, structured query language
(SQL), that is the standard for database interoperability. SQL is the foundation for all of the
popular database applications available today, from Access to Oracle.

8.4.1 Database Transaction
A database transaction comprises a unit of work performed within a database management system
(or similar system) against a database, and treated in a coherent and reliable way independent of
other transactions. Transactions in a database environment have two main purposes:

1. To provide reliable units of work that allow correct recovery from failures and keep a
database consistent even in cases of system failure, when execution stops (completely
or partially) and many operations upon a database remain uncompleted, with unclear
status.

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