Characteristics of a good database design
The purpose of this report is to typically discuss about characteristics of a good database design and a quality design. Main reasons behind writing this record is really as part of execution of Stanwell parish method the necessity for a database program was determined by several committees.
Our committee is in charge of the design a database for record the runners participated on the twelve-monthly Fell race. The brand new broadband internet access facility is effective in creating these different facilities.
A database could be identified as a couple of records or data files which happen to be logically related. Computer based databases are usually organised as you or multiple amount of tables. A desk consists of group of rows and columns.
Relational model is a robust and commonly used method for organising data. The desk design of the data source reflects the quality of the database.
The ideas of normalization should be considered always when making a effective database. Objectives of normalization are follows.
- Minimising data redundancy
- Minimising data restructuring
- Minimising I/O by redesign purchase sizes
- Enforcing referencing integrity.
When designing an efficient database following approaches and concepts are essential to consider.
- Identifying an entity as a logical collection of items linked to the stated data source. And an attribute is a descriptive or quantitative feature of the entity.
- The physical counterpart of the entity is definitely a database table and the physical counterpart of the attribute is the column.
- Primary key is determined as an attribute which identifies each instance of an entity uniquely.
- The logical website link between two entities may be the relationship.
- When the principal key of a parent entity exists in a child entity, it really is called as a foreign key.
- There will be two types of relationships, Identifying and non Identifying. Identifying interactions are when primary key element of the mother or father entity exists in the primary key of the kid entity. In non identifying relationships primary primary of the parent major exists in the kid entity but not as a part of primary key of the kid entity.
- To understand the type of the relationship between the parent and kid entities, cardinality is effective. Four types of cardinalities are
§ 1 to 0 or more
§ 1 to 1 1 or more
§ 1 to 0 or 1
§ 1 to many
In designing a correct data source ER, EER and Use Case are actually useful modelling tools.
2. Need for data modelling
Data testmyprep model is an extremely useful program in communicating between coders and users of a database. Additionally it is helpful in identifying style issues and other complications before starting the actual design process. A info model is like a blueprint of a recently constructing setting up. Builders will newer start building a large construction without a proper blueprint. Even though changes are made during the developing process, the basic foundation remains the same.
Importance of ER diagrams in the design
ER diagrams falls right into a category of data modelling.ER diagrams display entities in a database and associations between tables. This graphical representation helps to understand how the database works with the interactions and dataflow. Regardless of what size or small the data source is, the ideas of entity and marriage are the same.
ER diagrams have 3 basic components.
For an example, in the Fell Race database, Race can be recognized as an entity and calendar year of the Race could be identified as an attribute. An entity corresponds to a table of the database and features corresponds to the columns of that particular table.
Most common errors that can happen when making an ER diagram can be stated as,
- Missing constrains
- Missing keys to any entity type
- Unexpressed constrains because of bad design
- Associating attributes with incorrect entry types
- Putting invalid constrains
- Misuse of subclasses
- Using foreign keys instead of relationships
EER Diagrams in modelling
EER diagrams are also a similar sort of software to ER diagrams aside from some little differences. It really is identified as enhanced model of ER diagrams.
EER = ER + hierarchical interactions Hierarchical relationship means marriage between Super school and subclass, the IS A romance.
The next step is usually transferring the ER diagram or EER diagram into well organized relations. A relational desk is made up of one or more info tables or relations. The mapping ought to be done in a way in order to avoid data duplication. That is called data redundancy.
Data redundancy can become a problem for many reasons.
- Entering same data again and again is a waste products of time.
- Data redundancy escalates the probability of occurring errors
- Errors may appear when retrieving data.
- Disk space is definitely wasted.
- Affect the performance of the entire system
- When updating, deleting info, multiple rows is highly recommended.
Normalization may be the process used in order to avoid data redundancy.
Importance of Use Case diagrams in the design
Use cases are used in the analysis stage of the design process. Main aim for of drawing a work with case is to identify the system functionality. Use situations separate the system into use conditions and actors.
Use cases stand for the integration of actors and the machine. An actor is defined as something with behaviour. An actor testmyprep could be a person or another program.
According to the Fell Race system actor can be someone who uses the machine to enter info (user).
3. Importance of a good database design
Mainly a good, effective database design helps the development group to reduce the costs and time taken for the overall development. By creating a good data model and following a correct process, helps the development workforce to understand user requirements plainly and accurately.
4. Is the correct database design necessarily an excellent design?
The remedy is no. A correct database design isn’t always an excellent design. But an excellent design should always be a correct design.
In a quality design, rather than putting data over multiple files, data is stored in a single logical unit. This reduces the duplication of data. The non duplication of data helps to maintain data integrity. Likewise a quality design is helpful in maintain the security of data. Info can be managed properly trough a quality database design. Finally a quality design is a design and style that helps to increase the performance of the database. A correct database design works, but an excellent design will help improve the performance of the data source.
An affective and quality database design helps the development workforce to reduce time and the entire cost of the system development process. By taking a correct approach to database style helps the team to understand the user requirements correctly and deliver a system the user desires. A good database design will also help increase the efficiency of the machine.
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