Access 2007 - Basic Database Concepts
?What is a Database
A database is a collection of
information that has been organised so that the information is easy to access
and display in different ways. Databases are used everywhere: at work, in the
home, in schools, and leisure facilities. Real world database examples are as
obvious as a telephone directory, an encyclopaedia, or even a library
Computerising a Database
The advantage of any database is
that information is easy to find because it is well organised. If the database
is computerised, then information retrieval is faster and more accurate still.
More importantly, it is possible to manipulate the information in the database
in different ways. A paper database can only be viewed in one way - the way it
was printed. In a computer database, information can be re-sorted and filtered
to display different views of the data. For example, with a computer telephone
directory, you could easily create a list of the telephone numbers of people in
your street. The main disadvantage of a computerised database is that designing
and creating an efficient database takes time. Also, a database has to be
maintained carefully, to ensure that it is used properly and that the data
stored is accurate
Databases and spreadsheets
A database and spreadsheet can both
be used to store and present data. For example, in a spreadsheet you can enter
data into a list, with structures much like that of a database application.
However, a dedicated database application is much better at storing a very
large amount of data. Also, databases have sophisticated tools for ensuring the
integrity of data as it is entered and to keep it securely, for retrieving data
quickly, based on specified criteria, and for presenting data in different
ways. It is common practice to use a spreadsheet to import data from a database
to analyse it or perform calculations.
Database Terms
The following terms are used to speak about
databases.
Database A database is a collection
of objects used for storing and managing information. In Access, a database is
stored on disk in an .MDB file . The MDB file saves the database objects and
the data they contain
Object
An object (in Access) means a
database component, such as a table, query, form, or report.
Table
A table is the place in the database where
data is stored. A table consists of one or more fields, which define what
information is kept for each record. Fields are represented by columns and each
field must have a unique name. A record represents one entry in the database -
the collection of fields make up the information you want to store about the
"thing" the record represents. Each record is a row in the table. In
the example overleaf, the table is storing information about the products a
company sells. You can see fields for an ID number, Category, the name
of the Product, the Amount for each unit of the Product, the Price per unit,
and the Stock Level. Each product sold by the company has a record in the table
At its simplest, data in a table is
shown as a datasheet. A table looks similar to a spreadsheet in that it is divided
into columns and rows, but its use and structure is different to a spreadsheet.
Each column in the datasheet represents a field. Each row in the datasheet is a
record.
Form
A datasheet shows all of the
records in a table at once. A form is a more user-friendly way of presenting
data.
A form usually displays data in the table one record at a time, with
fields arranged neatly on-screen. In the example below, you can see all the
fields making up the table, whereas with the datasheet you would have to scroll
the window to see Reorder
Level and Discontinued.
Query
Queries
are a tool for selecting and sorting data to make it easier to work with. For
many database operations, you may not want to see all records at the same time,
or to analyse data, you may wish to see how many records fit conditions you
specify (criteria). For example, which products have a price greater than
£10.00? Queries can be used to update and modify data as well as to look at it.
You can also use expressions in queries to perform calculations on data.
Report
Tables, queries, and forms can be printed as
seen on the screen, but reports allow data to be presented in a more structured
format. Reports based on queries print only the selected fields and records
that the query produces. Reports can also include calculations and summaries of
the data printed
Review
Questions Basic Database Concepts
Answer the following questions:
What type of database object would you use to add a record?
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How could you display information from just three fields in a database, with records
sorted in
descending order?
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What two advantages do computer databases hold over a paper database?
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