Database Systems. Bence Molnár

Transcription

1 Database Systems Bence Molnár

2 Info Bence Molnár K s 2 credits 1 test at week 12th 1 database project as homework

3 Objectives Basic knowledge about database systems Usability examples in civil engineering Introducing the MS Access software

4 Summary Theory of databases Basics and concepts Relational algebra Database design In practice SQL

5 Homework Specification: Design: definition of goals alphanumeric database Implementation: Create and upload the designed DB and perform analysis year=2015&lang=en

6 Further information Jeffrey D. Ullman - Jennifer Widom: A First Course in Database Systems (3rd Edition), Prentice Hall, 2007

7 Do we need/use databases?

8 Databases in every days Where are they used? everywhere... shopping, traveling, communication, web surfing (social media), sports, etc... Relevance Knight Capital Group (trade, 2012)...

9 Daily routine

10 Daily routine (2010)

11 Daily routine (2013)

12 Top worldwide databases (2007) Rank Name Role 1 Max Planck Institute Scientific research 2 NERSC Scientific research 3 AT&T Telecommunication 4 Google Internet services 5 Sprint Telecommunication 6 ChoicePoint Government, social and buisines information sharing 7 YouTube Video sharing 8 Amazon Online shop 9 CIA Secret agency 10 USA Library of Congress Library services

13 Progress: Spreadsheets to Databases

14 How does a spreadsheet look like? Name Address Frank Young Phone Education Company Budapest Mechanical engineer Tools Suite Co. Steave Tromp Cegléd Civil engineer Road builder Inc. Scout Briar Budapest Economist Money First Ltd. Emmet Morty Budapest Secondary school Road builder Inc

15 How does a spreadsheet look like? Column=Attribute Name Address Frank Young Phone Education Company Budapest Mechanical engineer Tools Suite Co. Steave Tromp Cegléd Civil engineer Road builder Inc. Scout Briar Budapest Economist Money First Ltd. Emmet Morty Budapest Secondary school Road builder Inc Row=Record, Tuple Cell=Field

16 Easy with spreadsheets Fill up (upload data) Add or remove a column Add or remove a row Calculate derived cells

17 Problems of spreadsheets High amount of data Lot of rows Lot of cells Searching Joining sheets or tables Consistency Special searches and queries

18 Database? Use databases in case of: High amount of data, Several type of attributes are defined, Demand of consistency, Input data type is inhomogeneous, Demand of complicated queries. Once tools are available, databases are created even small

19 Basics

20 Basics Data: (database stored) value. Static: unchanged till manual or automatic intervention (eg. Bank balance). Data itself is meaningless. Information: kind of data, that inherits meaning during the analysis. Dynamic: Based on the stored data. Propagated by processing and analysis. Dynamically changes based on new records. Summarize: data is the stored values, information is derived from data.

21 Basics Metadata: data describing data. Describes the file definitions, structure and handling method to improve the usability of archived data. For databases: names of tables in database, corresponding size, number of rows, etc.

22 Basics Database model: A database model is a type of data model that determines the logical structure of a database and fundamentally determines in which manner data can be stored, organized, and manipulated. The most popular example of a database model is the relational model (or the SQL approximation of relational), which uses a tablebased format.

23 DB vs. DBMS Database (DB): structured and stored data. Database Management System (DBMS): Tools (programs) for manipulating, storing, creation of data. In practice: databases are created with DBMS. Every DBMS uses limited number of database model types, so once a DBMS is chosen, it determines the used model as well.

24 Examples DB: see at slide in introduction DBMS: MS Access, SQL Server (Microsoft) PostgreSQL (Open Source) MariaDB (GPL, Open Source) MySQL (GPL, commercial, Oracle) Oracle (commercial, Oracle) CouchDB (Open Source, Apache) SQLite (Open Source, Richard Hipp)

25 Database levels - physical The lowest level of abstraction describes how a system actually stores and access data on hard drive. The physical level describes complex low-level data structures in detail.

26 Database levels - logical The logical level of abstraction describes what data the database stores, and what relationships exist among those data. This means the table definitions like attributes, attribute types and table connections.

27 Database levels - view Views are data representations through the defined data model. Type and number of views are determined by the specification and demands.

28 History

29 History 1960's (first official appearance Oxford dictionary: data-base) History is introduced connected database model. through 1962, the

30 Early database models hierarchical

31 Early database models network

32 Relational model 1969 Edgar Codd (1980-) Flexible, Widely Easy easy to expand used to overview Connections Clear are not defined at model level mathematics background: set theory (relational algebra)

33 Object-Oriented Model Not widely used in DBMS as the storage and queries are not efficient Idea comes from the object-oriented programming languages; therefore it's used in integrated programs and databases.

34 NoSQL databases Not only SQL Nowadays getting popular Differs in terms of storage solutions Queries are not based on SQL Examples: documenting databases: storing half structured data, inspired by web (2.0); graph databases.

35 Graph databases

36 Relational model - basics Structural concept: Table (realization of connection/relation), Row (record, tuple), Attribute/properties/column (cell), Special cell (e.g. multi-valued). Cell properties (NOT NULL, DEFAULT) combined, derived,

37 Rellational model - basics Value types: numeric (smallint, int, bigint, float, double, ), text/string (varchar(x), text), Logical (boolean), NULL: not 0, not white-space (' '), not empty string (''), eg.: name prefixes, special types: binary, geometric, unique.

38 References Wikipedia J. D. Ullman J. Widom: A First Course in Database Systems

39 Thank You! Questions?