In this unit. We will teach you how to make your data
useful. Currently, the data we've just collect is just a "raw data".
It still in the form of long strings of letters, Numbers and Symbols which is
quite useless because we can't actually find the correct info and some can be
missing.
Useful database needs to have some structure and meaning
attached to it to make it simpler, prevent mistakes, no errors and accurate.
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Database Components
"Files" or "table" - The whole set of
database
"Record" - A data collection in which one specific
type.
"Fields" - Labels of the heading/Column (Name of
the column)
Database Types
There are 2 types of database: Flat Files and Rational
Database.
Flat files Database - only a tables or files in whole
database.A flat file database is a database designed around a single table. The
flat file design puts all database information in one table, or list, with
fields to represent all parameters. A flat file may contain many fields, often,
with duplicate data that are prone to data corruption.
Flat files' Advantages:
- Simple and easy to make.
Flat files' Disadvantages:
- More space requires
- Errors can be occur easier (By human mistakes when type in
data)
- Takes more times to edit database.
Rational Database - Advanced Database. Will have 2 or more
files/tables which linked together. Mostly used by computer experts. A
relational database, on the other hand, incorporates multiple tables with
methods for the tables to work together. The relationships between table data
can be collated, merged and displayed in database forms.
Most relational databases offer functionality to share data:
Across networks
Over the Internet
With laptops and other electronic devices, such as palm
pilots
With other software systems
Rational Database's Advantages:
- Faster and controllable
- Less or none error occur
- Take less space (Also causes database processes faster)
Rational Database's Disadvantages:
- Much more complicates
- High ICT knowledge needed
- Error can be occurs badly if not an expert or supervised.
Here are some examples from the class work Diagram:
Here are some examples from the class work Diagram:
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This is how two or more tables linked together by a foreign key |
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Data Types |
| Identifying the data type in Access |
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| A closer look... |
Data types are types of each data such as text, numbers, date etc. The useful point for this is to narrow the chances for us to make mistakes. There are severals of them.
- Text : Only accept Alphabet, Numbers and Special characters
- Number : Only accept numbers,Can be seperated in to intergers and Real numbers
-----------------Integers are made up of whole numbers (numbers without decimals).
---------------- Integers can be both positive and negative values.
----------------------- Real numbers are those that include decimals.
-----------------------Real numbers can be both positive (above zero) and negative (below zero).
- Date/Time : Only accept time and date
----------------Date and Time data can be shown in many different ways. The most common ways are shown in the table below:
- Hyperlink : Only accept the "link" we've browse
- Boolean : Only accept "Yes" or "No"
- Drop down lists : use for creating drop down list (similar to VLOOKUP in excel)
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| Type Of data in Access |
Review & revise
Why data is important: It's important that the database knows what type of data it's using, for two main reasons.
1. data such as number are stored differently to text.
2. As a result of being stored differently, this determines what operations can be carried out.
Using the database
You have now reached the stage where you have a complete record structure for a flat file database. The structure includes: Field name, and field types.
Sorting
Now to put it into use, you will have to learn how to sort it first !
To Sort a data is simple to rearrange it, in other words to out the records in a different order. We often put them in alphabetical order of filename. In database you can rearrange them and displayed them in orders, though;
- by date created
- by size
- by type
Searching
when you search , you expected to see only a selection of records from the original list. This is called subsets. For example you might have numerous number of records of your client's data, you might want to displayed the ones that are under the age of 16. When you issued the search command, the list reduced - you will see the ones that are under the age of 16.
As for database, the "search" part is to located records that fit your search criteria. In database terminology this involves creating a Filter.
Criteria and Operators
The conditions used to define a sort or a search are called Criteria. When sorting records , the data is rearranged according to our criteria. When searching, criteria concerns the ACTUAL content of the fields-One criterion, & two criteria.Searches can be made quite complex, yet detailed and precise. this is done by the operators:
- < (less than)
- > (more than)
- = (equal to )
- <= (less than or equal to )
- >= (morethan than or equal to )
then it will be compared to logical Conditions (AND, OR, NOT, LIKE) to refine the search.
Wildcards
as well as operators and logical conditions, there are two more search tools. These are called Wildcards , used to search through text fields.
An asterisk (*) is used to represent a one or more character in a string of text, and a question mark (?) represent a single character.
For example:
- Searching a student name it could be "White" or "Whyte" therefore we put it as "wh?te"
- Searching for a transport , something that involves with ship (like warships, battleships,etc. ) so you out it as " *ship"
Difference between searching and sorting: Searching allows you to find data that meets specific criteria. Sorting allows you to organize that data, based upon the rules you choose
How to "Database"
Part I: Introduction
Part II: Producing Labels
Part III:Creating a new record structure in a database
Part IV: Adding Validation
Part V: Running a query
Part VI: Creating a Report
Database Search Criteria
Some tips before you do your database...
