Revision
0 likes362 views
This document provides an overview and summary of key concepts related to advanced databases. It discusses relational databases including MySQL, SQL, transactions, and ODBC. It also covers database topics like triggers, indexes, and NoSQL databases. Alternative database systems like graph databases, triplestores, and linked data are introduced. Web services, XML, and data journalism are also briefly summarized. The document provides definitions and examples of these technical database terms and concepts.
Revision
- 1. ADVANCED DATABASES REVISION 1
- 2. REVISION TACTICS • Watch the videos from emails and moodle • Take notes • Follow these slides • Visit the web resources • Learn the keywords and concepts • Learn SQL • Use Cmap tools to link concepts /t erms • Revisit your patchwork
- 3. THE BUILDING BLOCKS TERMS AND CONCEPTS YOU SHOULD KNOW BY NOW… • XML • NoSQL • Graph • ODBC • Relational Database • MySQL • SQL • Linked Data • RDF • Trigger • Database Index
- 4. REVISION TOOL: CMAP TOOLS • http://cmap.ihmc.us/download/ • Tool for creating concept maps
- 5. TOPICS • Relational Databases (MySQL) • SQL • Triggers • Transactions • Webservices • XML • NoSQL / Alternative Database systems
- 6. RELATIONAL DATABASES MYSQL
- 7. RELATIONAL DATABASES ‘FORMALLY DESCRIBED TABLES’ • This module focused on MySQL: an Open source implementation of a relational database • Oracle, PostgreSQL, SQLite • Most patchworks should be done in MySQL (Triggers, indexs) • ODBC Component • Looked at alternatives: NoSQL (Not Only SQL), Graph Database, triplestore
- 8. RELATIONAL DATABASES: SQL (STRUCTURED QUERY LANGUAGE) • Language to manage data in relational management systems • Should be examples in your patchwork CREATE TABLE example_autoincrement ( id INT NOT NULL AUTO_INCREMENT PRIMARY KEY, data VARCHAR(100) );
- 9. RELATIONAL DATABASES TRANSACTIONS
- 10. TRANSACTIONS ‘UNIT OF WORK PERFORMED WITHIN A DATABASE MANAGEMENT SYSTEM’ • A transaction is a unit of work • Treated independently of each other
- 11. TRANSACTIONS ‘UNIT OF WORK PERFORMED WITHIN A DATABASE MANAGEMENT SYSTEM’ • In a relational database each transaction must have ACID properties • Proposed in 1970s • Key idea in relational databases • Atomicity • Consistency • Isolation • Durability • A transaction need to reach these 4 goals to be reliable
- 12. TRANSACTIONS ‘UNIT OF WORK PERFORMED WITHIN A DATABASE MANAGEMENT SYSTEM’ • Atomicity • All or Nothing • both pay for and reserve a seat; OR neither pay for nor reserve a seat. • Consistency • Only ever writes valid data • Isolation • Transactions will not interfere with each other • Durability • Once a transaction is complete it will always remain. Even in the event of a powerloss
- 13. TRANSACTIONS ‘UNIT OF WORK PERFORMED WITHIN A DATABASE MANAGEMENT SYSTEM’ • Sometimes we can’t use ACID • CAP THEORY • A theory by Eric Brewer in 2000 It is only possible to have 2 of the following in a distributed computer system • Consistency • Availability • Partition Tolerance
- 14. TRANSACTIONS ‘UNIT OF WORK PERFORMED WITHIN A DATABASE MANAGEMENT SYSTEM’ • Consistency All the nodes in the distributed system have the same system • Availability A guarantee that every requests get a response (even if it fails) • Partition tolerance If a node fails then the whole system will continue to operate
- 15. TRANSACTIONS ‘UNIT OF WORK PERFORMED WITHIN A DATABASE MANAGEMENT SYSTEM’ • So what do large companies/distributed computer systems do? • Use alternatives to ACID • Most popular alternative to ACID is BASE • Basic Availability • Soft State • Eventual Consistency For when it’s OK to use stale data, and it’s OK to give approximate answers. http://www.cs.berkeley.edu/~brewer/cs262b-2004/PODC-keynote.pdf
- 16. TRANSACTIONS ‘UNIT OF WORK PERFORMED WITHIN A DATABASE MANAGEMENT SYSTEM’ • Basically Available • Availability is achieved through multiple data stores rather than one fault tolerant system • Soft state • Consistency is abandoned, or at least is the problem of the application and not the database • Eventual Consistency • At some point in the future data will converge so that data on nodes is in a consistent state
- 17. RELATIONAL DATABASES: ODBC OPEN DATABASE CONNECTIVITY
- 18. RELATIONAL DATABASES: ODBC OPEN DATABASE CONNECTIVITY • Standard database access method • SQL Access group • Independent of database system http://shivasoft.in/blog/microsoft/csharp/what-is-odbc-and-oledb-interview- question/
- 19. RELATIONAL DATABASES: TRIGGERS • SQL statement or SET of statements fired when an event occurs. (for example INSERT, UPDATE and DELETE) CREATE TRIGGER `event_name` BEFORE/AFTER INSERT/UPDATE/DELETE ON `database`.`table` FOR EACH ROW BEGIN -- trigger body -- this code is applied to every -- inserted/updated/deleted row END; http://www.sitepoint.com/how-to-create-mysql-triggers/
- 20. DATABASE INDEX • improves the speed of data retrieval operations • Stops searching through each row one by one • Created on columns • Most Common • B-tree (MySQL default?) • Hash Really good -> http://20bits.com/article/interview-questions-database-indexes http://dev.mysql.com/doc/refman/5.5/en/index-btree-hash.html
- 21. B TREE INDEXING • B-Tree • Stores data in logical way • We want people younger than 13.. Look left
- 22. INDEXS • Hash Tables • Speeds up = or <=> • Not > or < B-tree vs Hash Tables http://dev.mysql.com/doc/refman/5.5/en/index-btree-hash.html
- 23. WEBSERVICE
- 24. WEBSERVICE • A way to communicate between systems (machine to machine interaction) • Service Provider • Service Requester
- 25. WEB SERVICES • 3 types of nodes • Registries (Service Broker) • Providers • Requesters
- 26. XML • XML: • EXtensible Markup Language • Designed to store and transport data • (whereas html was designed to display data) http://www.w3schools.com/xml/xml_whatis.asp
- 27. WEB SERVICES ADVANTAGES • Advantages • Work outside of private networks • Interoperability • Could be the content processing/logic module in Three-tier architecture?
- 28. WEB SERVICES DISADVANTAGES • Availability? • Based in a stateless (unreliable?) protocol :http • Security?
- 29. NOSQL
- 30. NOSQL • Not Only SQL • Databases that are not like relational database management systems • Not built around the idea of tables • Not likely to use SQL • Usually built around BASE style principles (not ACID) • Examples : Graph Databases
- 31. GRAPH DATABASE • Every Element has a pointer to another element
- 32. TRIPLE STORE • Similar to Graph Data • Built to store and retrieve triples (David eats chocolate bars, Mars is a chocolate bar, etc etc) • Data is stored in a standardized way (such as RDF/XML) • Has a querying service (sparql)
- 33. LINKED DATA • Method of publishing structured data • Different datasets can be interlinked • Built on the following technologies • URI’s • HTTP • Structured formats RDF/XML • Sometimes this data is stored in triplestores • Served by website (content negotiation) • Like prod.cetis.ac.uk • Could have a relational database behind it • Example: dbpedia
- 34. LINKED DATA • Linked Data is made up of triples! • Subject, predicate object • David -> eats -> cake • David (Subject) Eats (Predicate) Cake
- 35. DATA JOURNALISM • Explosion of visual analytic tools • Gephi • Visualise a network/graph • Visually Identify complex patterns / markets