-It is a collection of information that is organized so that it can easily be accessed, managed, and updated.
-It is a logically organized collection of data helpful in easy search and retrieval of data
-A database isn’t necessarily contained on a computer. A telephone directory is still a huge book sitting next to your phone.
Database
examples of commonly used databases might be:
- Address book
- Library catalogue
- Telephone directory
- Stock list
examples of the sort of information that can be kept in a database:
- Inventory control
- Payroll systems
- Personnel
popular relational database management systems include:
- Microsoft Access
- Filemaker
- Microsoft SQL Server
- MySQL
-Oracle
Drawbacks of using file systems to store data:
- Data redundancy and inconsistency
- Security problems
- Data isolation multiple files and formats
- Difficulty in accessing data
- Concurrent access by multiple user
-Integrity problems
Advantages of Database
-Improved availability
-Minimized redundancy:
-Accuracy
-Program and file consistency:
-User-friendly:
-Improved security:
One of the principle advantages of a DBMS is that the same information can be made available to different users.
Improved availability
- The data in a DBMS is more concise because the information in it appears just once.
- This reduces data redundancy, or in other words, the need to repeat the same data over and over again.
-Minimized redundancy:
-Accurate, consistent, and up-to-date data is a sign of data integrity.
-DBMSs foster data integrity because updates and changes to data only have to be made in one place.
-The chances of making a mistake are higher if you are required to change the same data in several different places than if you only have to make the change in one place
-Accuracy
- Using a database management system, file formats and system programs are standardized.
- This makes the data files easier to maintain because the same rules and guidelines apply across all types of data. The level of consistency across files and programs also makes it easier to manage data when multiple programmers are involved.
-Program and file consistency:
Data is easier to access and manipulate with a DBMS than without it. In most cases, DBMSs also reduce the reliance of individual users on computer specialists to meet their data needs.
-User-friendly:
-DBMSs allow multiple users to access the same data resources. This capability is generally viewed as a benefit, but there are potential risks for organization.
-Some sources of information should be protected or secured and only viewed by select individuals. Through the use of passwords, database manage-ment systems can be used to restrict data access to only those who should see it.
-Improved security:
- It is responsible for storing data in the database.
- Database tables consist of row (record) and columns ( field)
Table
-It is a named unit of information
-A discrete piece of information that is part of a record. Each column in the Access table is a different field
Field
-It is a group of fields within a table that are relevant to a specific entity.
- A row in a table that contains information about a particular person, place, or thing.
Record
RELATIONAL DATABASE
- It is a field (or fields) that uniquely identifies the record. Sometimes you can assign a natural primary key.
- Each column or set of columns in a table that contains unique values is considered a candidate key
The primary key
-It is the process of applying a series of rules to ensure that a database achieves optimal structure.
- It the process of organizing data to minimize duplication
-Its refers to the process of creating an efficient, reliable, flexible, and appropriate “relational” structure for storing information
Normalization
-All columns (fields) must be atomic which means no repeating items in columns
- To achieve this, all columns in a table must be atomic and no repeating values.
-This means, for example, that you cannot store first name and last name in the same field.
- The reason for this rule is that data becomes very difficult to manipulate and retrieve if you store multiple values in a single field
First Normal Form
- All non-key columns must be fully dependent on the primary key.
- In other words, each table must store data about only one subject.
Second Normal Form
- a table must meet all the requirements for first and second normal forms, and all non-key columns must be mutually independent.
-Remove columns that are not dependent upon the primary key.
Third Normal Form
Enumerate the database relationship
- One-To-One Relationships
- One-To-Many Relationships
- Many -To- Many Relationships
- It can exist between any two tables in which a row in the first table can be related o only one row in the second table and a row in the second table can be related only row in first table.
-these least likely type of relationships to be implemented in a relational database. - This relationship can be use because one table would contain too much data, or perhaps you would want to separate data into different tables so you could set up one table with a higher level of security
One-To-One Relationships
- a row in the first table can be related to one or more rows in the second table, but a row in the second table can be related to only one row in the first table.
- The user must develop this type of relationship by adding a table called a junction table. You relate the junction table to each of the two tables in one-to-many relationships.
One-To-Many Relationships
-When you define a dimension, typically each fact joins to one and only one dimension member, whereas a single dimension member can be associated with many different facts.
-the user must develop this type of relationship by adding a table called a junction table. You relate the junction table to each of the two tables in one-to-many relationships.
Many -To- Many Relationships
