Collection of Education/collectionofeducationcarat1997.iso/COMPUSCI/PC_LEARN.ZIP/PART2.EXE/DATABASE.TUT

Text File | 1992-01-25 | 11KB | 195 lines

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                    USING DATABASES - THAT FEELING OF POWER

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       It is said that there are three classes of programs which
       interest business and home computer users:

       Word processors help you talk about money. Spreadsheets help you
       keep track of money. But databases help you MAKE money. Given
       that provocative insight, let's probe deeper . . .

       A database program allows you to store, sort, organize, retrieve
       and prepare reports about information in a logical way. Facts,
       figures and ideas all benefit from careful organization,
       retrieval, sorting and storage. Spreadsheets come with a formal
       layout (rows and columns) and are best used for examining
       relations BETWEEN items and MANIPULATING the results.

       Databases require a more STRUCTURED format for the information.
       They are, however, more flexible in layout and allow more
       reporting variety on the information contained in the database.
       Most databases work with records or forms (like 3 x 5 cards).
       You can specify the information contained: names, addresses,
       client types and so on. Each form within a database always
       contains the same information. Just like filing cards which
       always contain the same entries.  A good way to think of a
       database is a shoebox with many baseball cards - each with the
       same headings (field names). Each card of course contains
       different information. An important term used in describing and
       working with databases is the FILE which is a collection of
       similar RECORDS like a shoebox full of baseball cards. A RECORD
       is the data items which are duplicated to make up the file (each
       baseball card.) Each record has FIELDS which are items within
       like the date of birth for an individual baseball player. Lower
       still is the CHARACTER is simply an individual number, symbol or
       alphabet letter. Characters are sometimes called character
       strings. Common character data might include names, product
       labels, numeric identification or other data. In addition some
       fields are fixed in length and must be set prior to database use
       (e.g., PC FILE:DB) while others allow flexible length character
       strings to be entered (e.g., Microsoft Works). These limits are
       set by either or both the available disk space and available RAM
       memory space.

       But many databases extend still further. New database products
       include capabilities for graphing relationships between sets of
       data, producing summaries and even working with pictures.
       Another useful feature is error checking within a database which
       means that if the field is preset to only allow zip codes, if a
       dollar amount or state abbreviation is mistakenly entered, the
       computer will beep and pause for another try. Further databases
       can be preset to only work in some fields with real numbers or
       integers depending on data needs.

                          An example database screen:
                  =================================================

                            ---- CUSTOMER LIST ----

                     name:                      product used:
                     address:                   frequency of use:
                     city:                      social security no:
                     state:                     birthday:
                     zip:                       category:
                     remarks:                   date of first contact:

                   =================================================

       The above is a simple screen layout for a database customer file
       or christmas card mailing list. Many databases can also list
       information in columns or a list view) and in many different
       report styles. The exciting idea behind databases is that you
       can retrieve a single record or groups of records very quickly.
       You could, for example, locate all customers who use a
       particular product. Or perhaps all customers in the same city
       over a certain age (calculated from the birthday field) who
       purchased from your store within the last year.

       There are two general styles or types of database programs:
       single file (also called flat file or file manager type) and
       multi-file (also called relational). Single file type databases
       operate on one set of information at a time while multi-file
       (relational) databases work with many interrelated sets of data
       at once. An example of single file would be cards in a recipe
       box; the cards could be sorted, searched and checked one at a
       time. A relational, multi-file database could interrelate a set
       of recipe cards to a set of cooks and a set of diners and a set
       of dates available for dinner - all at the same time! Complex,
       but useful . . .

       Generally, single file databases are easy and relatively
       inexpensive (as well as being suitable for beginners). Examples:
       Microsoft Works, Pc-file, Q & A and Reflex.  Multi-file
       databases are more complex, and more expensive. Examples: dBase,
       Paradox and Rbase.

       Some databases store excess data during program operation on
       disk, while others store data only in limited RAM memory during
       operation and then place data on disk when the computer is shut
       off. Disk based databases can hold more information but are a
       little slower searching and sorting. RAM based databases are
       fast but can only hold a finite amount of data since they must
       contain everything within RAM. Generally many relational
       databases are disk based while flat file, simple databases are
       RAM memory based.

       Reporting capabilities are also of interest. A database must be
       able to "let you see" or REPORT the data in different ways. Some
       format possibilities are columns, cross tabs, graphs and
       extracted lists. The idea is flexibility in printing of reports.

       The sorting of data is crucial. A sort refers to the reordering
       of data on the disk or within RAM memory. You might wish to sort
       your database into a list by zip code order to take advantage of
       bulk mailing rates. Later you might wish to resort the same data
       into a list with high income customers are the top and low
       income customers at the bottom. The useful possibilities are
       endless. Disk based database programs usually store a special
       INDEX file which cross references the main data and keeps track
       of where individual records are located. This allows for faster
       searching and sorting since the smaller index is examined rather
       than churning through all the records to find or delete data.
       Multiple indexes refers to the capability to have separate
       indexes on one database. Each index reflects a different sorting
       pattern.

       Searching or selecting data can be tedious or easy depending on
       the program. Some programs like Q & A allow you to recall data
       by asking in simple english sentences or phrases. This may be
       easy at first but limits greater intricacy later. Most programs
       allow for expressions which can search at a refined level but
       require phrases such as:

       STATE="WA" or STATE="OR" and INCOME >="$45,000"

       This is a bit more "mathematical" in appearance but isn't hard
       for the beginner to master with practice. This more
       "mathematical" approach to searching allows pinpoint accuracy.

       Modern