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Introduction to Oracle and SQL

Introduction to Oracle and SQL - Relational database...

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Relational database fundamentals Learning objective After completing this topic, you should be able to identify the basic principles of the relational model for databases. 1. Relational databases Although certain aspects of the Oracle 10g Database are case and spacing insensitive, a common coding convention has been used throughout all aspects of this course. This convention uses lowercase characters for schema, role, user, and constraint names, for permissions, synonyms, and table names (with the exception of the DUAL table), and for column names shown in code. Uppercase characters are used for keywords and functions, for view, table, schema, and column names shown in text, for column aliases that are not shown in quotes, and for data dictionary views. The spacing convention requires one space after a comma and one space before and after operators that are not Oracle-specific, such as +, -, /, and <. There should be no space between an Oracle-specific keyword or operator and an opening bracket, a closing bracket and a comma, between the last part of a statement and the closing semicolon, or before a statement. String literals in single quotes are an exception to all convention rules provided. Please use this convention for all interactive parts of this course. A database is an organized collection of related data. The database structure may be simple or complex, depending on the nature of the information it contains and the needs of database users. To manage your databases, you use a database management system (DBMS) - a program that stores, retrieves, and modifies data in databases in response to your commands and specifications. Historically, hierarchical and network database models were used in database design. But while these constitute an improvement on simple flat-file database models, they have significant limitations. Oracle 10 g uses a relational database management system (RDBMS), which has advantages over previous database models. Relational database s are structured using entities attributes relationships relational operators rules and constraints entities
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An entity is anything that may be the subject of a query. For example, in a database used by human resources departments, commonly used entities include employees and departments. attributes Entities are defined and qualified by their attributes . In the case of the employee entity, its attributes might include employee ID number, name, and job title. Attributes can be compulsory or optional – that is, you may have to specify a value for a particular attribute, or you may not. relationships Associations between entities are called relationships . For example, the employee and department entities might be related on the basis of the department ID attribute, which they share.
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