Data that resides in a fixed field within a record or file is called structured data. This includes data contained in relational databases and spreadsheets.
Structured data first depends on creating a data model – a model of the types of business data that will be recorded and how they will be stored, processed and accessed. This includes defining what fields of data will be stored and how that data will be stored: data type (numeric, currency, alphabetic, name, date, address) and any restrictions on the data input (number of characters; restricted to certain terms such as Mr., Ms. or Dr.; M or F).
Structured data has the advantage of being easily entered, stored, queried and analyzed. At one time, because of the high cost and performance limitations of storage, memory and processing, relational databases and spreadsheets using structured data were the only way to effectively manage data. Anything that couldn't fit into a tightly organized structure would have to be stored on paper in a filing cabinet.
Structured Data, SQL and Unstructured Data
Structured data is often managed using Structured Query Language (SQL) – a programming language created for managing and querying data in relational database management systems. Originally developed by IBM in the early 1970s and later developed commercially by Relational Software, Inc. (now Oracle Corporation).
Structured data was a huge improvement over strictly paper-based unstructured systems, but life doesn't always fit into neat little boxes. As a result, the structured data always had to be supplemented by paper or microfilm storage. As technology performance has continued to improve, and prices have dropped, it was possible to bring into computing systems unstructured and semi-structured data.
Unstructured data is all those things that can't be so readily classified and fit into a neat box: photos and graphic images, videos, streaming instrument data, webpages, pdf files, PowerPoint presentations, emails, blog entries, wikis and word processing documents.
Semi-structured data is a cross between the two. It is a type of structured data, but lacks the strict data model structure. With semi-structured data, tags or other types of markers are used to identify certain elements within the data, but the data doesn’t have a rigid structure. For example, word processing software now can include metadata showing the author's name and the date created, with the bulk of the document just being unstructured text. Emails have the sender, recipient, date, time and other fixed fields added to the unstructured data of the email message content and any attachments. Photos or other graphics can be tagged with keywords such as the creator, date, location and keywords, making it possible to organize and locate graphics. XML and other markup languages are often used to manage semi-structured data.
Oracle Corporation – Oracle Database 11g (Proprietary); MySQL (GPL or Proprietary)
Sybase – Adaptive Database Server; SQL Anywhere (Proprietary)
IBM – DB2, Informix Dynamic Server (Proprietary)
FileMaker – FileMaker (Proprietary)
Microsoft – SQL Server, Access
Hewlett-Packard – HP NonStop SQL (Proprietary)
Apache – Apache Derby (Apache License)
PostgreSQL Global Development Group – PostgreSQL (PostgreSQL open source license)
All of the above databases work with Microsoft Windows. All except the Microsoft products also support at least one other operating system (Mac OSX, Linux or Unix).
Structured Data Technology
SQL has been a standard of the American National Standards Institute since 1986. It is managed by InterNational Committee for Information Technology Standards (INCITS) Technical Committee DM 32 – Data Management and Interchange (http://standards.incits.org/a/public/group/dm32). The committee has two task groups, one for databases and the other for metadata. HP, CA, IBM, Microsoft, Oracle, Sybase (SAP) and Teradata all participate, as well as several federal government agencies. The database projects are listed here - http://www.incits.org/tc_projects/dm32.2.pdf - and the Metadata projects here - http://www.incits.org/tc_projects/dm32.2.pdf. Both of the committee project documents have links to further information on each project. SQL became an International Organization for Standards (ISO) standard in 1987. The published standards are available for purchase from the ANSI eStandards Store – webstore.ansi.org – under the INCITS/ISO/IEC 9075 classification.
Information on setting up and managing a relational database is available at Database Journal (www.databasejournal.com), including expert tutorials on Microsoft SQL Server, Oracle, IBM DB2, Microsoft Access and MySQL.