Lesson 6.1: Introduction to the Management of Data

Question 1

A database table

Answer 1

A database table, also known as a datasheet, is composed of records and fields that hold data. Data is stored in records. The records are represented as rows in a table with related information.

Question 2

Database Management Systems

Answer 2

A typical database application has two major layers: an application layer and a database management layer. The application layer communicates with the end user and can be fairly complex. For example, when end users access a database through a website, the application layer consists of programs and services within a server that queries the database on behalf of the client.

The application layer of a database does not directly manipulate the data. After the application software receives a request from a user, it uses the database management system (DBMS) as a tool to obtain the results. If the request is to add or delete data to or from the system, the DBMS alters the database after receiving the request through the application layer. If the request is to retrieve information, it is the DBMS that performs the required searches.

The DBMS is similar to an operating system in that it supports the application software and the data.

Question 3

Flat-File Databases

Answer 3

A DBMS contains routines that translate commands into the actions required by the actual data storage system. This conceptual view of the database is called a database model. Flat-file, relational, hierarchical, and object-oriented are some of the most common database models.

A flat-file database stores data in a plain text file. Each line of the text file holds one record. Fields are separated by delimiters like spaces or commas. Because a flat database uses a simple structure, it cannot contain multiple tables.

Question 4

Hierarchical Databases

Answer 4

The hierarchical database is one of the oldest database models. Data is organized in a tree structure, much like an organizational chart. There is one parent for each record, with optional nodes, forming sub-trees called segments. Access to the data is predictable and restricted to the paths in the trees.

Question 5

Relational Databases

Answer 5

Relational databases contain database tables that can be joined together in logical ways. Because data is stored in relational tables, each record has a unique identifier, such as a product identification number or user name. This unique identifier, referred to as a primary key, creates the relationship among tables. A field may be marked as the primary key on one table but also be found on another table. When this happens, a relationship called a foreign key is created.

The role of some attributes is to interrelate tables in a way that establishes meaningful relationships relating to their real-world interactions.