brief database dictionary

A tiny glossary for database terms

database: A collection of related information stored in a
structured format. Database is often used interchangeably with the term
table (Lotus Approach, for instance, uses the term database instead of
table). Technically, they're different: a table is a single store of
related information; a database can consist of one or more tables of
information that are related in some way. For instance, you could track
all the information about the students in a school in a students table.
If you then created separate tables containing details about teachers,
classes and classrooms, you could combine all four tables into a
timetabling database. Such a multi-table database is called a relational database.

data entry: The
process of getting information into a database, usually done by people
typing it in by way of data-entry forms designed to simplify the
process.

dbms: Database management system. A program
which lets you manage information in databases. Lotus Approach,
Microsoft Access and FileMaker Pro, for example, are all DBMSs,
although the term is often shortened to 'database'. So, the same term
is used to apply to the program you use to organise your data and the
actual data structure you create with that program.

field: Fields describe a single aspect of each member of a table. A student
record,
for instance, might contain a last name field, a first name field, a
date of birth field and so on. All records have exactly the same
structure, so they contain the same fields. The values in each field
vary from record to record, of course.

flat file: A
database that consists of a single table. Lightweight database programs
such as the database component in Microsoft Works are sometimes called
'flat-file managers' (or list managers) because they can only handle
single-table databases. More powerful programs, such as Access,
FileMaker Pro and Approach, can handle multi-table databases, and are
called relational database managers, or RDBMSs.

index:
A summary table which lets you quickly locate a particular record or
group of records in a table. Think of how you use an index to a book:
as a quick jumping off point to finding full information about a
subject. A database index works in a similar way. You can create an
index on any field in a table. Say, for example, you have a customer
table which contains customer numbers, names, addresses and other
details. You can make indexes based on any information, such as the
customers' customer number, last name + first name (a composite index
based on more than one field), or postal code. Then, when you're
searching for a particular customer or group of customers, you can use
the index to speed up the search.

key field:
You can sort and quickly retrieve information from a database by
choosing one or more fields to act as keys. For instance, in a students
table you could use a combination of the last name and first name
fields as a key field. The database program will create an index
containing just the key field contents. Using the index, you can
quickly find any record by typing in the student's name. The database
will locate the correct entry in the index and then display the full
record.

primary key: A field that uniquely
identifies a record in a table. In a students table, a key built from
last name + first name might not give you a unique identifier (two or
more Jane Does in the school, for example). To uniquely identify each
student, you might add a special Student ID field to be used as the
primary key.

record: A record contains all the information about a single 'member' of a table. In our students table, each
student's details (name, date of birth, contact details, and so on) will be contained in its own record.

relational database:
A database consisting of more than one table. In a multi-table
database, you not only need to define the structure of each table, you
also need to define the relationships between each table in order to
link those tables correctly.

table: A single store of
related information. A table consists of records, and each record is
made up of a number of fields. You can think of the phone book as a
table: It contains a record for each telephone subscriber, and each
subscriber's details are contained in three fields – name, address and
telephone.