Managing Files: Basic Concepts • Data storage hierarchy - levels of data stored in a computer: – Database – an organized collection of integrated files. – File – a collection of related records. – Record – a collection of related fields. Often called a row. – Field – a unit (individual piece) of data consisting of one or more characters (bytes). Often called a column. • Character (byte) – a letter, number, or special character. • Key field – a field that is chosen to uniquely identify a record so that it can be easily retrieved and processed. Field Name Rec ord Fie ld
Transcript
Managing Files: Basic Concepts
• Data storage hierarchy - levels of data stored in a computer:
– Database – an organized collection of integrated files.
– File – a collection of related records.
– Record – a collection of related fields. Often called a row.
– Field – a unit (individual piece) of data consisting of one or more characters (bytes). Often called a column.
• Character (byte) – a letter, number, or special character.
• Key field – a field that is chosen to uniquely identify a record so that it can be easily retrieved and processed.
Database: An organized collection of related (integrated) files. A database is a collection of related data or facts.
• DBMS: Database management system (DBMS) – programs that control the structure of a database and access to the data.
Field
Record
Field Name
• DBMS is a collection of programs that control the database.
• Advantages of DBMS:
– File sharing
– Reduced data redundancy
• Data redundancy – situation in which the same data fields appear in many different files and often in different formats.
– Improved data integrity
• Data integrity – measure of how accurate, consistent, and up-to-date data is.
– Increased security
Database Models
The four most common Database Models
• 1. Hierarchical database – fields or records are arranged in related groups, resembling a family tree, with child (lower-level) records subordinate to parent (higher-level) records.
• 2. Network database – similar to a hierarchical database, but each child record can have more than one parent record.
• Relational database – a database which relates (connects) data in different files through the use of a key field, or common data element.
4. Object-oriented database – database which uses “objects” (software written in small, reusable chunks) as elements within database files
SQL (Structured Query Language) – the standard language used to create, modify, maintain, and query relational databases.
• Common Corporate DBMS and also called database softwares
