Usually embedded in another language or tool for database access and manipulation
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3 basic sql operations
project, restrict, join
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what is refernetial integrity?
efers to the accuracy and consistency of data within a relationship. In relationships, data is linked between two or more tables. This is achieved by having the foreign key
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what do relational database systems try to do?
try to enforce referential integrity rules to ensure that relationships between coupled tables remain consistent.
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so....
When one table has a foreign key that points to another table, we may not add a record to the table with the foreign key unless there is a corresponding record in the linked table
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Normalisation
Store data in different tables and then link them together using foreign keys
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Denormalisation
merge tables by eliminating foreign keys
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why denormalise?
Denormalisation allows database management system (DBMS) to store redundant data so that the query response may be optimised • Denormalisation must base on real life activities of an organisation
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continued....
multiple users, Tables may be stored in different physical locations (hard drives) , frequently query and access
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what is loaded into a data warehouse?
Transaction data are loaded into the warehouse only when the activity on them has been completed.
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what does relational design not apply to?
Relational design does not apply to a data warehousing system as the relations are stable
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what does data warehouse store?
Data warehouse stores consolidated, denormalised tables that contain historical data
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what is data mining?
the process of exploring data (usually large amounts of data in data warehouses) to discover useful information - DISCOVER HIDDEN RELATIONSHIPS AND PATTERNS
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1. An example of a data mining query
- Customers who bought product #21 also bought what other products?
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2. An example of a data mining query
During a promotion of product A, did product B also have an increased sales volume?
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3, An example of a data mining query
what are the What are the profiles of customers who dined in Michelin-starred restaurants?
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HOW IS DATA MINING USED IN DATA AND FINANCE? (3)
– Detect patterns of fraudulent credit card use – Assess credit card customer loyalty – Predict spending of key customer segments
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How is data minnig used in health care? (3)
– Predict hospital visits from past patient behaviours – Identify successful medical treatments for illnesses – Identify behavioural patterns of high-risk customers
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how is data minig used in supply chain managment?
o Assess reliability of suppliers o Predict inventory fluctuations
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how is data mining used in marketing?
o Identify purchasing patterns o Predict response to various forms of marketing
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surface web is........
– indexable by search engines
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so what does this mean?
search engines organise information before a search to enable super-fast responses to queries
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the deep web....
is Not visible to search engines
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what do search engines use?
web crawlers - it is an Internet bot that systematically browses the World Wide Web, typically for the purpose of Web indexing.
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