ORACLE 11G Learn from scratch-20141202

1.2.4, Database schema

1, three level mode

(1), Concept mode

Also called pattern, is a description of the logical structure of the global data in the database, is the public view of the whole user. It mainly describes the concept record type of the data and its relationship, and also includes some semantic constraints between the data, and its description can be defined by the DDL in the DBMS.

(2), external mode

Also known as sub-mode or user mode, it is a description of the logical structure and characteristics of the local data that the database user (including the application and end user) can see and use, a data view of the database user, and a logical representation of the data related to an application.

(3), internal mode

Also known as the storage type. is a description of the physical structure and storage of the data, defining all the internal record types, the organization of indexes and files, and the details of data control.

2, Level two image

(1), external mode/mode image

Each external mode of the database has an external mode/pattern image, which defines the corresponding relationship between the external pattern and the pattern, which is generally described in the external mode.

(2), mode/internal mode image

is unique because the database has only one mode and internal mode. It exists between the pattern and the inner mode. It is the correspondence between the data global logical structure and the storage structure. Generally described in the internal mode.

1.2.5, Data Model

is a form of the database used to provide information representation and manipulation of the means of the formal framework, the database is used to abstract the real world tools.

(1), Conceptual data model

is an objective-oriented, user-oriented model, independent of the specific database management system, independent of the specific computer platform.

(2), logical data Model

is a database system-oriented model, which is the intermediate level between the conceptual model and the computer.

Hierarchical model: Use "tree structure" to represent the connection between data.

Relational model: Use "Two-dimensional table" to represent the relationship between data.

Mesh Model: Use "graph structure" to represent the connection between data.

Object-oriented Model: Use "Object" to represent the connection between data.

(3), physical data model

It is a model for the representation of computer physics.

The three main elements of the data model: data structure, manipulation, and integrity constraints.

1.2.6, data integrity constraints

(1), Entity integrity

If property A is the primary property of the basic relationship r, property A cannot take a null value.

(2), referential integrity

Defines the rule of reference between the outer code and the main code.

(3), user-defined integrity

is a constraint on a particular relational database that reflects the semantic requirements that the data involved in a particular application must meet.

1.2.7, online transaction processing, and online analytical processing

Online transaction processing OLTP: Mainly used to complete the business processing of database application system. Improved productivity and quality of work

OLAP on-line analytics: It enables analysts, managers, and executives to quickly, consistently and interactively observe information from all aspects to achieve the goal of deep-dive data. Processing from leadership and decision-making, comprehensive, real, and intuitive to reflect the various aspects of the camp activities.

1.2.8, Data Warehouse

Pay a large amount of data information storage.

Characteristics:

(1) Theme -oriented

(2) Integrity

(3) Stability

(4) Time variability

ORACLE 11G Learn from scratch-20141202