The important concepts of this week
This chapter is providing us knowledge about Data Degine, how to degine the database.In this system analysis phase, we are able to create data flow diagrams and identified data elements,data floes,and data stores to build a logical degine for the information system,there is physical design for planning for data organization,storage and retrieval.It is based on data design concepts and terminology about file base systems,database systems including web based database,how to create entity relationship diagram,what symbols we have to use for the diagrams,how many types are of entities are there.Entity in ERD diagram is not the external entity in DFD.They are opposite of each other.Entity is something about which the business want to store data,there are three types of entities strong entity,weak entity and associative entity.Attributes are the properties of entity,four types of attributes are useable single or primitive attribute, group attributes or compound/complex,single value attribute and multi valued attribute. .Carditality is a process to show relation betwwen two entities. There are three types of relationships:- one to one relationship,a one to many relationship, a many to many relationship and how to use cardinality notation.The common method of cardinality notation is called crow’s foot notation because of the shapes,which include circles,bars and symbols indicate various possibilities.A single bar indicates one,a double bar indicates one and only one,acircle indicates zero,and a crow’s foot indicates many.While using data design terminology we usetables,field.recordsand during this various key fields are use to organize,access and maintain data structures. The four types of keys are use:-Primary Keys,Secondary Keys,Candidate Keys,Forgine Keys.Sometimes the Primary Key must be the combination of two fields, in that case the primary key is called as combination key, this combination key is also known as composite key,a concatenated key or a multi valued key.There is Referenttial Integrity for validity check,its a set of rules that avoids data inconsistency and quality problems but in relational database referntial integrity means that a forgine key value cannot be entered in one table unless it matches an existing primary key in another table.The concept of normalization that change change the complex data to a tabular form.Three normal form are there.Using codes during data design like sequence codes,Block sequence codesand Alphabetic codes.Two types of database modelling is discuss in this phase:- Relational databases and Object oriented databases,various types of data storages and access are used like data warehouse, is an integrated collection of data tyhat can include unrelated information,no matter where can be stored in the company because it can link various information system and databases.Data mining is using for retriving data, its a software looks for meaningful patterns and relationships among data.There are two types of storage logical and physical.A logical record is a set of fields values that describes a single person, place,thing or event, and physical storage involves a physical records, or block which is the smallest data unit that can be handled by the operating system.The system reads or writes one physical records at a time.The data storage formats are EBCDIC(Extended Binary Coded Decimal Interchange Code)is a data storage method used on most mainframe computers, and ASCII(Amercian Standard Code for Information Intrchange)which is used on most minicomputer and personal computer.EBCDIC and ASCII require one byte of storage for each character,numeric digit,or symbol.ODE is a relatively recent coding method that represents characters as integers.Unicode is uses 16 bits per character, which allows it to represnt more than 65,000 unique characters.Binary storage format offers more efficient storage of numeric data,compared to character based format,which requires one byte per alphanumeric character. THese copncepts are very useful for successful and future growing business Some problems are there with cardinality in understanding with minimum and maximum cardinality.
