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Slide 2: 

Data base system:-A database is an organized pool of logically-related data. Data is stored within the data structures of the database. Data Base Management System:-is a set of computer programs that controls the creation, maintenance, and the use of the database in a computer platform or of an organization and its end users.

Slide 3: 

Data Dictionary:- It is a centralized repository of information about data such as meaning, relationships to other data, origin, usage, and format. It is a document describing a database or collection of databases

DATA BASE SCHEMA- Definition : 

DATA BASE SCHEMA- Definition A database schema is a collection of meta-data that describes the relations in a database A schema can be simply described as the "layout" of a database or the blueprint that outlines the way data is organized into tables. The schema of a database system is its structure described in a formal language supported by the database management system (DBMS)

Slide 5: 

In a relational database, the schema defines the tables, the fields, relationships, views, indexes, packages, procedures, functions, queues, triggers, types, sequences, materialized views, synonyms, database links, directories, Java, XML schemas, and other elements. Schemas are generally stored in a data dictionary

Levels of database schema : 

Levels of database schema Conceptual schema Logical schema Physical schema Schema object

Conceptual schema : 

Conceptual schema A conceptual schema or conceptual data model is a map of concepts and their relationships. It describes the things of significance to an organization (entity classes), about which it is inclined to collect information, and characteristics of (attributes) and associations between pairs of those things of significance (relationships).

Logical schema : 

Logical schema A Logical Schema is a data model of a specific problem domain expressed in terms of a particular data management technology. It is a map of entities and their attributes and relations Without being specific to a particular database management product, it is in terms of either relational tables and columns, object-oriented classes, or XML tags.

Physical schema : 

Physical schema It is a particular implementation of a logical schema It is a term used in relation to data management how physically data would be stored on disk drives. That is the domain of the physical schema.

Schema object : 

Schema object It is a logical data storage structure A schema is a collection of schema objects. Examples of schema objects include tables, views, sequences, synonyms, indexes, clusters, database links, snapshots, procedures, functions, and packages Oracle stores a schema object logically within a table space of the database. The data of each object is physically contained in one or more of the table space’s data files.



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