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Zayna Khan 10/03/2010 SECTION 5 Data Types Data Type Example Boolean Text Integer Real Date Yes/No Andy Conda 16 1.456 25/10/2010 Term File Record Definition A set of related records (either written or electronic) kept together The data shown is a group of related data items - all of the data refers to one student: Zayna Khan. A group of data like this is called a record. In single record, we can see that it is made up of a number of different data items. The individual items are referred to as fields In most databases, one of the fields is used to uniquely identify each record (the value of this field must be different for each record). This special field is called the key field. Field Key Field Flat-file versus Relational Databases Flat-file database Relational database 1 table Several tables that are linked by foreignkey relationships Less data redundancy as same information is not repeated twice Same piece of information may be repeated lots of times, Data redundancy very common Data inconsistency quite likely to occur Data inconsistency is impossible Zayna Khan 10/03/2010 With reference to “primary key”, “foreign key” and “relationship” explain what is meant by “data redundancy” and “data consistency” and explain how relational databases address the problems associated with each (6) A flat-file database consists of one table. A relational database comprises a number of tables that are linked by foreign-key relationships. In a flat-file database the same piece of information may be repeated lots of times. However, a relational database would only store it once, in a separate product table. The fact that a flat-file database stores the same information several times is an example of data redundancy. Data redundancy can also lead to data inconsistency, for example if a new row is created in a flat-file database and the product's price is entered wrongly. Relational databases avoid data consistency problems by only storing each piece of information once. It is still possible to enter a "wrong" price for a product, but it is impossible for the price to be inconsistent if the database is designed properly. Define the following: Analogue data Analogue data can be any value within a defined range. For example, an analogue sound level can have any loudness between zero and the maximum recorded and any frequencies between the highest and lowest recorded. A traditional watch face is an analogue output and a vinyl record is an example of an analogue storage device. Digital data Digital data is made up of the two binary numbers, 0 and 1. Text, music, images, video etc all have to be converted into digital data (digitised) before they can be processed and stored by a computer. Digital data is transferred as a stream of on/off or high/low pulses and can have many different forms such as electrical, light, radio, infrared, microwave, etc. These pulses have only two states representing the two binary numbers. In an electrical digital signal for example, the voltage pulses are either on, representing a 1, or off , representing a 0. Give four reasons why data needs to be converted from Analogue to Digital Digital data is easier to communicate between computers because it is already in a format that can be processed Digital data is faster to communicate between computers Analogue data cannot be processed by a computer so it must be converted into digital data by an interface. I can’t think of another one