Table of content
Table of content
Chapter 0 Introduction
Chap 1 Models of Data storage and its developments
I-Flat file system
II-hierarchical theoretical account
III-Network theoretical account
IV-Relational theoretical account
IV-a-Properties of a relational database direction system ( RDBMS )
V-partial decision
Chap 2 Database modeling and design ( ER diagram, calling conventions and design )
I-Database design attacks
I-a-Top-down attack
I-b-Bottom-up attack
II-Business procedure and regulations
III-understanding the entity-relationship theoretical account
III-a-Entity
Chapter 3 RDBMS and execution
Drumhead
Chapter 0 Introduction
Databases are at the fireplace of any information system architecture of any concern presents. By assisting to pull off gathered information, databases are now seen as a decisional tool in companies and by implementing, they can transport out of import alterations in concern direction. Those alterations vary from concern to concern. For an online-selling company for case, it can be used to cognize the wonts of their clients in order to supply them with the best merchandises or the 1s they are more likely to purchase. By making so, it will cut down the clip made by each client online and as a benefit for the company, it will cut down the traffic to the web waiter and easy manage more on-line clients.
For our instance survey, which is related to the direction of the pupils at LSC group, such a database will efficaciously heighten the manner student’s informations are stored and exploited. My study will so hold these aims to supply with up to day of the month and inside informations information about database design for LSC group. In order to accomplish that end, we will travel through different parts and in a first clip, I will do a comparing between assorted informations storage theoretical accounts such as hierarchal theoretical account, web theoretical account and relational theoretical account which will take to the pick of a theoretical account to utilize. Then will follow a survey of two different databases design attack which is top-down attack and bottom-up attack. Before reasoning, we will plan our database and supply the concern regulations and different calling convention of it.
Chap 1 Models of Data storage and its developments
Databases have known a long development which is spread over the last 40 old ages now. That development goes from level file system to object-oriented database with more characteristics, flexiblenesss and complexnesss. In this first chapter, we will concentrate on different database theoretical accounts chiefly the hierarchal theoretical account, the web theoretical account and the relational theoretical account.
- Flat file system
Flat file system is the earless informations storage method. Data where merely entered in a file. All the tabular arraies were stored in a individual file without any relationship between them. That theoretical account gave immense work to the plans and coders who wanted to entree stored informations because there was no standard among different company who handle the file. So a written plan was utile for a individual type of file and non with the other 1. Furthermore, that storage system does non hold a procedure of look intoing or to avoid redundancy, so information was enormously duplicated. Those restrictions lead to an betterment in informations storage which is the hierarchal theoretical account.
- hierarchal theoretical account
Hierarchical database theoretical account is a theoretical account that uses a one-to-many relationship between its elements or tabular arraies. Hierarchical theoretical account is besides good defined as an inverted tree with the one side or ‘parent ‘ at the top of it and kids at the underside, each kid can be a parent every bit good.
Figure
Compared to the file-based system, hierarchal theoretical account had a batch more of advantages in term of informations construction which is chiefly relationship between tabular arraies. Lets us see as illustration our instance survey to clearly explicate it. The hierarchal theoretical account will enable a semester, which will play the function of the one side, to hold many classs, which are kids here. We can so go on with a class that has many topics.
“Figure”
By making so, informations are easy managed and it is easy to recover informations from the database.
However, that theoretical account has besides its restrictions. We saw antecedently that a class have many topics and harmonizing to the hierarchal theoretical account, a topic can non be taught in different classs. By and large talking, it means that a kid can non hold more than one kid and that is a restriction in existent unrecorded because a kid can hold a venereal parent and an adoptive 1 who are both its parents. This so introduce the many-to-many relationship which will be improved in other database theoretical account. Another restriction with that theoretical account is data duplicate that largely occurs in the many or child side.
- Network theoretical account
Network theoretical account improves hierarchal theoretical account by adding many to many relationship among elements. This is made by the creative activity of nexus between records. A record here is a twosome of properties, each of them keeping merely one information value. So records are seen here as entity compared to relational theoretical account and links as dealingss. By associating two records, the whole will do a set.
One of the chief jobs with web theoretical account is the figure of nexus established among records which increase the figure of sets. For case, allow presume that a pupil can take many capable and a topic can be taken by more than one pupil. They will be a demand to explicitly make for each pupil ‘s record all the links to the topics he is taking and vice-versa.
Figure.
This efficaciously creates many-to-many relationship among records but it besides make the figure of nexus and sets to pull off addition as the figure of record additions.
- Relational theoretical account
Relational theoretical account adds more characteristics to the old theoretical accounts. Alternatively of holding each record stored and managed individually like in the hierarchal theoretical account, informations are organised in tabular arraies. Each tabular array incorporating properties of different types. Each of these properties hive awaying more than one information value. Data in a tabular array are organised in rows which make a record.
Fig demoing a tabular array, its properties and the records.
Relationss are established by associating records of different tabular arraies via a specific property known as the primary key. By making so, we can easy stand for different types of relation among tabular arraies such as one-to-one, one-to-many or many-to-many relationship.
IV-a-Properties of a relational database direction system ( RDBMS )
In order to systematically hive away and pull off informations, RDBMS has some belongingss or regulations to follow. Harmonizing to Stephen and Plews ( 2001 ) P 50-51[ 1 ], they define the undermentioned belongingss of a RDMS
“
- A relational database direction system must be able to pull off databases wholly through its relational capablenesss.
- All information in a relational database ( including tabular array and column names ) is represented explicitly as a value in tabular format.
- Every value in a relational database is guaranteed to be accessible by utilizing a combination of the tabular array name, primary cardinal value, and column name. This means that you need non cognize the physical location of the information, and that you can straight entree any row of informations in a database tabular array independently.
- The DBMS should supply support for the intervention of void values ( unknown or unsuitable informations ) , which are distinguishable from default values, and independent of any sphere.
- The description of the database and its contents is represented at the logical degree in tabular format and can hence be queried utilizing the database linguistic communication. This refers to metadata that is stored in the information in respects to the database itself. Metadata is informations about other informations.
- At least one supported linguistic communication must hold a chiseled sentence structure and be comprehensive. It must back up informations definition, use, unity regulations, mandate, and minutess.
- All positions that are theoretically updateable can be updated through the system.
- The DBMS supports set-level retrievals, inserts, updates, and deletes.
- Application plans and ad hoc questions are logically unaffected when physical entree methods or storage constructions are altered.
- Application plans and ad hoc questions are logically affected every bit small as possible when alterations are made to the tabular array constructions. Although, if a tabular array is split into two tabular arraies, the application will hold to be changed so that the appropriate columns are accessed from both tabular arraies.
- The database linguistic communication must be capable of specifying unity regulations to protect the information. These regulations must be stored in the online catalog, and can non be bypassed when informations is modified.
- Application plans and ad hoc questions are logically unaffected when information is first distributed or when it is redistributed. Distribution refers to how informations is stored on hardware devices.
- It must be possible to short-circuit the unity regulations defined through the database linguistic communication by utilizing lower-level linguistic communications.
“
- partial decision
Geting at the terminal of our chapter where we had talk about different database theoretical accounts, we have seen that there were a batch of betterments made from the hierarchal theoretical account to the relational theoretical account. These alterations and betterment are recapitulated in the undermentioned tabular array.
Table review.
Harmonizing to the above tabular array, I will take the relational theoretical account to plan and construct the LSC group database.
Chap 2 Database modeling and design ( ER diagram, calling conventions and design )
- Database design attacks
There are chiefly two attacks that govern any database design. Top-down and bottom-up attack. Let ‘s hold a expression at each of them and its features.
I-a-Top-down attack
The top-down attack intends to look at things in general and travel down to make the more specific 1s. Basically, we start by set uping all the things that the system will make like the dealing between the different existent entities of the existent universe. Then by working closely with the end-users, the analyst can find what is needed to be stored in the database.
Let ‘s demo how this attack could be used in the instance of a database design for a college. First, the analyst will do a list of all the elements that make off the college to be. I mean the school direction squad, the different sections, the instructors, the pupils, the classs offered by the college and their several topics. Then we can travel to set up the duty of each of them which can take to the relation that will look in the terminal system. Finally, the analyst can interview some of these entities to hold more inside informations about their functions.
I-b-Bottom-up attack
Bottom-up attacks view database design as traveling from an initial analysis of lower-level conceptual units, such as properties, and so traveling towards an acceptable logical informations theoretical account through logical groupings of associated properties. To remain with the same instance of the instance of a database design for a college, the analyst will get down by entering all the different informations units that are managed by all the entities in the college such as the name, day of the month of birth age, sex and reference of the whole staff and pupils. Then, each related informations will be grouped to for entities.
Our instance survey is already expressed in term of informations aggregation. We already know the entities that need to be stored and even more some of their inside informations. We besides have a better apprehension of the relation among those entities stating us the informations flow generated. This eases our work since we don’t have to interview the end-user about their demand. So for that measure, we don’t need to utilize any database attack to find the entities, their properties and the relation bing among them.
- Business procedure and regulations
The concern procedure and regulations will assist us to clearly define function of each entity and the relation that exist among those entities.
Sing our given instance survey, we can set up the undermentioned concern procedure and regulations:
- every pupil enrolled at the college shall hold a name, a alone designation, a day of the month that he start the class and a phone figure ;
- each class offered by LSC group has an designation, a name, a continuance and a description
- it exist several semester and term, each of them holding a continuance and a name
- There is different capable delivered at the college. Each of them holding an identifier, a name, a consequence, the attending and the appraisals.
Furthermore, each pupil should be enrolled in a class to be considered as pupil of the college. A pupils can besides be enrolled in more than one class but non taking them at the same clip. Each pupil should take all the topics related to its class. Then, it becomes necessary to hive away informations about the consequences of the appraisals ( assignments and tests ) done by every pupil, their attending to every topic which will enable to find the attending for the whole class. Now about the footings and semesters, it is possible to hold more than one semester in each term but non the antonym. For each class they will take topographic point in many semesters.
With the above concern theoretical account, it is now possible to plan our database which is fundamentally the transition of the concern theoretical account into tabular arraies and dealingss.
- understanding the entity-relationship theoretical account
In the first chapter, after reexamining the different type and development of databases, we concluded by stating that we will utilize the relational theoretical account to plan our database. However, before doing the design, it is of import to specify the elements that made off the designated theoretical account.
III-a-Entity
Before planing our database, it is really of import to clearly specify
Conceptual, logical and physical database design
database development life rhythm
Chapter 3 RDBMS and execution
Decision
[ 1 ]Sir leslie stephens and Stew ( 2001 ) ,Database design,Sams.
