计算机学院 数据库系统原理 1 Introduction to Databases 杨宁 1/23

Contents What is Database Management System(DBMS) Something surrounding DBMS Key Concepts Key People 2/23

Concept of DBMS Database Management System (DBMS) provides efficient, reliable, convenient, and safe multi-user storage of and access to massive amounts of persistent data. 3/23

Concept of DBMS Database Management System (DBMS) provides efficient, reliable, convenient, and safe multi-user storage of and access to massive amounts of persistent data. 4/23

Concept of DBMS Database Management System (DBMS) provides efficient, reliable, convenient, and safe multi-user storage of and access to massive amounts of persistent data. 5/23

7 Key Aspects of DBMS Massive Persistent Safe Multi-user Convenient Efficient Reliable 6/23

7 Key Aspects of DBMS - Massive  Google holds petabytes of data gleaned from its crawl of the Web.  Pictures take much more space than texts. Repositories such Flickr store millions of pictures and support search of those pictures. Even a database like Amazon’s has millions of pictures of products to serve.  Videos consume more space than Pictures. Sites such as YouTube (YouKu) hold hundreds of thousands, or millions, of movies and make them available easily.  DBMS must be able to handle data residing outside of memory. 7/23

7 Key Aspects of DBMS - Persistent  Data in Databases outlives the programs that execute on that data.  Comparison with common computer programs Variables created by computer programs disappear after those programs finish. Data in database will be still there even after programs operating on that data stop. 8/23

7 Key Aspects of DBMS - Safe  Data in Databases always remains consistent, and won’t be lost or overwritten, regardless of what failure happens  Hardware failure  Software failure  Power outage  Malicious programs 9/23

7 Key Aspects of DBMS – Multi-user  Multiple users may access different parts of data  DBMS must ensure data to stay in a consistent state  Concurrency control  Tradeoff between consistence and performance 10/23

7 Key Aspects of DBMS – Convenient  Make it easy to work with large amount of data.  Physical Data Independence  The way that data is physically stored and laid out on disks is independent of  the way that programs logically think about the structure of the data.  High-level Query Language  Declarative In a query, you describe what you want out of the data but you don’t need to describe how to get the data out. 11/23

7 Key Aspects of DBMS – Efficient  Three import things in databases:  Performance  Thousands queries/updates per second 12/23

7 Key Aspects of DBMS – Reliable  Make it up all the time 13/23

Contents What is Database Management System(DBMS) Something surrounding DBMS Key Concepts Key People 14/23

Aspects surrounding Databases  Database applications may be programmed via frameworks  Ruby on Rails, etc.  DBMS may run in conjunction with middleware  Application Servers  Web Servers  Data-intensive applications may not use DBMS at all  Hadoop These are not the topics we are going to talk about in this class. ^_^ 15/23

Contents What is Database Management System(DBMS) Something surrounding DBMS Key Concepts Key People 16/23

4 Key Concepts of DBMS  Data Model  Schema versus data  Data definition language (DDL)  Data manipulation or query language (DML) 17/23

4 Key Concepts of DBMS – Data Model  Data Model: description of how the data is structured.  Relational Data Model: set of records  Semi-structured Data Model: XML (Hierarchical structure of labeled values)  Graph Data Model 18/23

4 Key Concepts of DBMS – Schema  Schema versus Data  Schema: type of variables  Data: value of variables  Schema: definition of the structure of database  Student(ID, Gender, College, Grade, … )  Schema does not change often, while data change rapidly. 19/23

4 Key Concepts of DBMS – DDL, DML  DDL: set up schema  DML: querying and modifying data 20/23

Contents What is Database Management System(DBMS) Something surrounding DBMS Key Concepts Key People 21/23

4 Key People of DBMS  DBMS implementer  Builds system  Database designer  Establishes schema  Database application developer  Programs that operate on database  Database administrator  Loads data, keeps running smoothly 22/23

Reading  Review: U/W ; S/K/S  Preview: U/W ; S/K/S /23