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What's in a database?
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What's In a Database?

In the last lesson we talked about what a database is, in this lesson we will talk about how a database is organized. If a person wants to be a successful searcher of databases she must understand how a database is organized.

Records

The largest unit of a database is referred to as a record. The database record provides the database user with a set of meaningful information. The following is an example of a MARC (MAchine Readable Cataloging) record from a library catalog.

This record is not the one that users of the library catalog see--it is the one that the cataloger created in the library database. Many databases use different user interfaces for the public. The public user interface is generally much easier to interpret (see the image below for the PALS public user interface for this record). We are showing you this technical user interface so that we can explain the concept of records, fields and subfields. What you see above is a record. It contains the information entered by the cataloger which describes the various aspects of the book entitled: IBM Dictionary of Computing.

Fields

Fields are units of a record that contain unique information. In the above example of the catalog record the fields are indicated by numbers. For example the title of the book is located in the 245 field. In a MARC record the 245 field always contains the title of the item. Other fields include:

• 050 Library of Congress Classification Number
• 092 Dewey Decimal Classification Number
• 260 Publisher Information
• 650 Library of Congress Subject Headings
• 700 Added Entry--Personal Name

Subfields

Fields are further broken down into subfields. Each subfield contains unique information. Subfields in the MARC record are indicated by the "#" and a lower-case letter. (Example: #b). Examples include:

• Subfield #b in both the 050 and 092 fields give the Cutter Number. The Cutter Number is added to both the LC and Dewey Call number.
• Subfield #c of the 245 field provides the name of the person responsible for authoring, editing or compiling the book.
• In the 260 field, subfield #b is where the name of the publisher is located, subfield #c is where the date of publication is located.
• In the 650 field, subfield #x is where a subheading of the Library of Congress Subject Heading is placed.

The following graphic is the same library record as it appears in the public user interface of PALS:

Notice that the field numbers have been replaced by field names. For example the 245 field has been replaced with the heading "Title." Most of the information in the MARC record is transferred to the PALS public display. The public display is much easier for the average person to read. Many databases work this way, i.e., the information that the user looks at is not the way it appears in the actual database.

What is important for the searcher to know is how the database is structured and which fields in the database can be searched. Database searches are performed by searching specific fields. Searchers must choose the appropriate field for their search or they will not find the information they need.