DATA TYPESSECTION V

DATABASE: Types of data

Id number Name Sex Form Tutor 18759 Noah Amu M 4AD Ms Arif 36729 Razia Mukadam F 3JU Mr Ali 51734 Shan Faizar F 6YD Ms Syed 51736 Ahmad Makhtar M 3JU Mr Ali

5 FIELDS (columns)

4 RECORD(rows)

20 ITEMS(each piece of data)

KEY FIELD(no other record can have the same item

DATA TYPES

DateNumeric:Integer

real

Yes/No LogicalBoolean

Text/Alphanumeric

Id number Name Gender Form Tutor Birthday Share 18759 Noah Amu M 4AD Ms Arif 15/8/2000 $9000 36729 Razia Mukadam F 3JU Mr Ali 6/9/2001 $8600 51734 Shan Faizar F 6YD Ms Syed 13/2/1999 $9800 51736 Ahmad Makhtar M 3JU Mr Ali 11/4/2001 $7800

Currency

DATA Verifaction and validation techniques

When data is input to a computer system, it is important to make sure that no errors are made. There are two types of checking that should be done on data input to a system:

Data Verification Data Validation

VERIFICATIONIs checking to make sure that what was input to the system was what was meant to be input.READ THROUGH or VISUAL CHECK

DOUBLE ENTRY

Have two people key the data in, then the computer can compare the two inputs and if they are not the same it can ask for data to be keyed in again.

This is the checking for errors by comparing entered data on the screen with the data in the original document

VALIDATION CHECKSExamples of different validation checks:

RELATIONAL DATABASES Consist of a number of separate tables which are related (this

is done using the primary key). Tables can also contain foreign keys that relate tables in the

database to one another. A foreign key in one table is a primary key in another.

It is possible to combine data from different tables to produce a report which contains the required information.

In relational database is faster data retrieval (recuperación de datos).

Is easy to expansion the database by adding extra data or new tables.

If data is changed in only one table, all other references to this data will then also be up date. This is called data integrity.

On the contrary, if a database is represented as a single table is called a FLAT Database

Sequential, serial or direct file

When the records in a database are in order of the key, is called a sequential file because the records are in sequence. Records are often stored in order of the key, either numerically or alphabetically, because this creates a file that is a lot easier to use and find things in.

If the file is in no particular order, or just in the order that the records were input (chronological order), it is called a serial file. Serial file are not very useful because they make it so difficult to find any information. They are kept when the file is not going to be used immediately. For example, a record of all the transactions that take place in a shop will kept as a serial file until the end of the day, when it may be converted to a sequential file in alphabetical order of items that were bought.

An alternative to converting a serial file to a sequential file is to create an index and allow the records to be kept randomly on the surface of a disk. Any record can be found without having to look through all of them, simply by going to the index and looking up the key in the index to find the location of the record. This is called a direct access file and it is used in the files where it is not possible to predict the order in which the records will be needed, such as the product records for the checkout in the supermarket.

DATABASE MAINTENANCE Updates or amend: When a piece of

information or item in one record is needed to be changed.

Insertions: When a new record will need to be inserted.

Deletions: When a record would need to be taken out of the file.