Database Technology Overview

Basic Concepts

1. Database and database management system

1) a database system consists of databases, hardware, software, and personnel.

2) databases are centrally managed and stored in computers for a long time. They are a collection of organized and relevant data.

3) The software includes the operating system, database management system, and applications.

4) Personnel

A system analyst and Database Designer

B application programmer

C. End User

D. Database Administrator

2. DBMS Functions

1) Data Definition database a structure description B integrity definition c security and confidentiality definition

2) database operation a search B insert c modify d Delete

3) database operation management a concurrency control B security check c access control d integrity check and execution e operation log organization management f Transaction Management g Automatic Recovery

4) data organization, storage, and management a includes data dictionary, user data, and access path. B. Determine the file structure and access method at the storage level. C connects data to improve the utilization of storage space.

5) database establishment and maintenance

6) Other functions

3. DBMS features

1) structured and unified database management.

2) high data independence.

3) data control function.

Security Protection of database.

B. Data Integrity.

C concurrency control.

D. fault recovery.

4. DBMS Classification

1) relational database system (RDBS)

2) Object-Oriented Database System (OODBS)

3) Object Relational Database System (ORDBS)

5. Database System Architecture

1) centralized database system

2) Client/Server Architecture

3) Parallel Database System

4) Distributed Database System

6. Three-Level schema of the database

1) concept Mode

2) External Mode

3) Internal Mode

4) Two-Level Image

Binary data model

1 concept

2. Three elements of the data model

3 E-R Model

4. Hierarchical Model

5. Mesh Model

6. Currently, the relational model is one of the most commonly used data models. In the relational model, tables are used to express the relationships between object sets and object sets.

7. object-oriented model

1) object and Object ID (OID)

2) Encapsulation

3) attributes of an object

4) Class and Class hierarchy

5) Inheritance

Three relational algebra

1. attributes and fields

2 Cartesian Product and relationship

3. concepts related to links

4. Link Type

5. Relational Database Mode

6 integrity constraints

7 relational operations

4. Introduction to Relational Database SQL

1. SQL database architecture

2. Basic Components of SQL

3. SQL data definition

4. SQL data query

5. SQL data update

6. SQL access control

7. Embedded SQL

5. Relational Database Standardization

1. function dependency

1) function dependency

2) non-trivial function dependency

3) Ordinary function dependencies

4) full function dependency

5) Partial function dependency (partial function dependency)

6) passing Dependencies

7) Code

A. Master code

B. Candidate code

C. primary attributes

D. Non-primary attributes

E. External code

8) function dependent systems

2. Standardization

3. Features of pattern decomposition and Decomposition

Six Database Control Functions

1. Transaction Management

A transaction is an operational sequence, either done or not. It is an inseparable logical unit of work.

1) SQL statements defined by transactions:

Begin transaction: Start of the TRANSACTION

COMMIT: transaction COMMIT

ROLLBACK: Transaction ROLLBACK

2) ACID)

Atomicity)

Consistency)

Isolation)

Durability)

2. database backup and recovery

1) Key Technologies of databases are establishing redundant data, that is, backing up data. The database recovery technology is how to restore the database to the correct state before the fault in a timely manner after a system failure occurs.

2) fault type:

A. Internal Faults

B. System Faults

C. Media faults

D. Computer Viruses

3) backup method

A. Static and Dynamic dump

B. Massive dumping and incremental dumping

C. Log Files

4) Recovery

A. Scan logs in reverse order to find the update operation of the transaction;

B. perform inverse operations on the update operation of the transaction;

C. Continue to repeat operations a and B until the start mark of the transaction;

5) database image

3. Concurrency Control

1) problems caused by concurrent operations

A. Lost changes

B. Non-repeated read

C. Read dirty data

2) concurrency control technology

A. Block

Exclusive lock: Write control. After the lock, only the blocked transaction can read and modify the data object, and other transactions cannot be read or written.

Shared lock: Read control. After blocking, all things can be read but cannot be modified.

B. Level 3 blocking agreement

Level 1 blocking protocol:

Level 2 blocking protocol:

Level 3 blocking protocol:

C. Active locks and deadlocks

D. serializability of concurrent Scheduling

E. Two block blocking protocols

Concept: all transactions must lock and unlock data items in two phases.

Get blocked

Release Block

F. Blocking Granularity

The size of the blocked object is called granularity. The blocked object has logical units (attributes, tuples, links, index items, the entire index, and the entire database) and physical units (data pages or index pages ).