abstraction in dbms

Record only, Original: https://beginnersbook.com/2015/04/instance-and-schema-in-dbms/Instance and schema in DBMS by Chaitanya SINGH | FILED Under:dbms Definition of Schema:design of a database is called the schema. Schema is of three types:physical

Physical layer: The lowest level of abstraction that describes how data is actually stored. The physical layer describes the complex underlying data structures in detail and is what the database vendors that develop the DBMS should study. Logical

? The DBMS (Database-management system) consists of a database and a program for accessing data, the basic goal of the DBMS is to provide a convenient and efficient way to access data, and for most enterprises, data is very important, so the DBMS

4. What are the categories of computers? What are their characteristics?Traditionally, there are three types: Large hosts, minicomputers, and minicomputers. Large hosts are generally high-performance parallel processing systems with large storage

The PDO full name is a PHP data object, which is an extension of the PHP connection database and is now widely used. PDO mainly solves the problem of providing a unified data access interface and operational layer for different databases. In order

From: web.tongji.edu.cn ~ Yangdydatabasepaper6.htmJDBC and ODBC Peng Xin Li Long return ---- Heterogeneous Database System is a database system composed of multiple heterogeneous member database systems, heterogeneity is reflected in the differences

1. DatabaseAs the name implies, database DB refers to the warehouse where the data is stored, except that the warehouse is located on the computer's storage device. Typically, this data is intended for an organization, department, or Enterprise,

51cto College, in the soft exam preparation season specially organized the "2014 Soft test-database Systems Engineering-Knowledge point explain" summary ", to help you pass the school smoothly! More software proficiency test Counseling and

1. Related Concepts and knowledge points 1. data Dependency: it reflects the constraint relationship between attributes within a link. It is an abstraction of the associations between attributes in the real world. It is a reflection of the inherent

I. Database Design Process Database technology is the most effective means of information resource management. Database Design refers to constructing the optimal database mode for a given application environment, establishing a database and its