A database is a collection of data for one or more uses. A database can be, as simple as, a text file with a list of names or, as complex as, a large relational database management system with in-built tools to maintain the data.
A database management system (DBMS) is a set of software tools that facilitates creating, maintaining and manipulating of an data within tables. A DBMS supports the structuring of the database in a standard format and provides tools for data input, verification, storage, retrieval, query, and manipulation.
A flat-file database program, such as Microsoft Excel, allow user to store data in files. Since the data in the files are not linked together a user can manage the data in one file at a time. Using a flat-file a user can create simple applications such as a mailing list database or managing financial data but the data between the files cannot be linked.
A relational database management system (RDBMS) stores and manages all its data in one or more virtual tables saved in database file(s). For example, to implement an accounting database system, one requires relational capabilities to link information that may be stored in one or more tables. Some of popular relational database software include Microsoft Access, Microsoft SQL Server, MySQL, Oracle, Sybase and DB2.
A relation database provide following tools to manage data in the database:
- SQL language to extract data from table(s).
- Forms to enter data into table(s).
- Report to view the results of a query.
Following are some of the advantages of a relational database:
- Potential for enforcing standards.
- Reduced application development time.
- Availability of up-to-date information to all users.
- Economies of scale.
- Data can be easily accessed.
- Data can be shared.
- Data modeling can be flexibility.
- Data storage and redundancy can be reduced.
- Data inconsistency can be avoided.
- Data Integrity can be maintained.
- Standards can be enforced.
- Security restrictions can be applied.
- Independence between physical storage and logical data design can be maintained.
- High-level data manipulation language (SQL) can be used to access and manipulate data.
A Relational database stores data in logical tables. Each table has a unique name and may relate to other tables in the database through one or more common attributes. The data stored in a table is organized in rows and columns. Each row in a table represents an individual record and each column represents a field.
For example, table 1 below displays 4 records and 3 fields. Each record represents the contact information of a person.
Table 1: PhoneBook
Most tables have one or group of columns that can be used to identify unique record in a table. When it a single column that can identify as a unique row, it call the primary key. For example, an Employees table might have an EmployeeID column that will contain unique row for the employee. This makes it easy to keep track of a record over time and to associate a record with records in other tables.
Foreign key column is a column in a table that is linked to primary key column(s) in another tables, thereby creating a relationship. For example, the Customer table might have a foreign key column called SalesRep that links to EmployeeID column, the primary key, in a Employee table.
A SQL query is a programing language that works with DBMS used to manage data in a database.
For example, to find all the records from the phone book (table1)with last name Smith, the SQL command will be as follows:
SELECT * FROM PhoneBook where LName = ‘SMITH’;
A form is used to enter or update data in a database. Following is an example of a form to enter information related to an Employee.
A Report tool is used to extract data from the database and display the data in a presentable format. A report can be used to present group of related record together and include summary totals for numeric fields. Reports can be created in a number of different presentation style. Some of the most popular design styles are tabular (the most common), single record, and multi-record ( for mailing labels). Following is an example of a report listing the student’s course, level and total score.
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