-
Database management system (DBMS): There is a collection of interrelated data and a set of programs to access these data. This collection of data is usually called a database.
-
Document processing system: Permanent records are stored in multiple different files, and people write different applications to take the records out of relevant files or add them to appropriate files
-
Data inconsistency: different copies of the same data are inconsistent
-
Consistency constraints: Each relational variable is subject to a series of consistency constraints, which can also be referred to as consistency constraints.
-
Data Abstraction
· Physical Layer: The lowest level of abstraction, describing how data is actually stored.
· Logical layers: the physical layer level slightly higher than the abstract description stored in the database What is the relationship between these data and what data. Describe the entire database through a small number of relatively simple structures.
**·** View layer: The highest level of abstraction, which only describes a certain part of the entire database. -
Example: A collection of information stored in the database at a specific time takes an instance of the database.
-
Mode: The overall design of the database is called the database mode.
a. Physical mode: describe the design of the database at the physical layer.
b. Logical mode: Describe the design of the database at the logical level. -
Physical data independence: If applications do not depend on the physical mode, they are said to have physical data independence, so they do not need to be rewritten even if the physical mode changes.
-
Data model: A data model is a collection of conceptual tools that describe data, data connections, data semantics, and consistency constraints.
a. Entity-Relationship Model: The entity-relationship (ER) data model is based on an understanding of the real world: the real world consists of a set of basic objects called entities and the connections between these objects . An entity is an opinion "thing" or an "object" that can be distinguished from other objects in the real world.
b. Relational data model: The relational model uses a collection of tables to represent the relationship between data and data.
c. Object-based data model: The object-oriented data model can be regarded as the ER model with the addition of encapsulation, method (function) and object identification Expansion after the concept.
d. Semi-structured data model: The semi-structured data model allows those same types of data items to contain data definitions with different attribute sets. -
Database language
a. Data definition language (DDL): is a language that describes the database schema and other characteristics (create table...)
b. Data manipulation language (DML): allows users to access or manipulate those organized in accordance with a certain appropriate data model Up data (select...from...where...)
c. Query language: -
Metadata: Metadata is data about data
-
Application: A program that interacts with the database in some way.
-
Standardization: Generating a collection of relational patterns is for us to store information without unnecessary honor, and at the same time to easily retrieve data.
-
Data dictionary: stores metadata about data structures, especially data patterns.
-
Storage manager: The storage manager is a component that provides an interface between the underlying data and applications in the database system and the queries submitted to the system.
-
Query processor: Enables database users to obtain high performance while working at the view level without having to bear the burden of understanding the physical level details of the system implementation.
-
Transaction: A collection of operations that complete a single logical function in a database application.
a. Atomicity: Either all happen or not happen at all (analog primitives)
b. Failure recovery: detect system failures and restore the database to the state before the failure occurred.
c. Concurrency control: control the mutual influence between concurrent transactions to ensure database consistency (analogous to the concurrent execution of processes when understanding) -
Data mining: discover knowledge in a database in a certain way
-
Database Administrator (DBA): The person who centrally controls the system is called the database administrator.
The above is summarized from the sixth edition of the original book "Database System Concepts"