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CS 111 – Nov. 17

CS 111 – Nov. 17. Enterprise databases Goals Examples Many-to-many relationship Restricting one’s view of entire database Design considerations Concurrency Commitment Homework #2 due Nov. 29. Goals. Retain and please customers Attention to detail Share data across company

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CS 111 – Nov. 17

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  1. CS 111 – Nov. 17 • Enterprise databases • Goals • Examples • Many-to-many relationship • Restricting one’s view of entire database • Design considerations • Concurrency • Commitment • Homework #2 due Nov. 29

  2. Goals • Retain and please customers • Attention to detail • Share data across company • Allow employees to “view” the portion of the database relevant to them • Quick response to employee or customer query • Customers can interact with database via Web site • Also: allow concurrent access • Distributed database • Client capability at point of sale • Server capability at HQ • Don’t keep all data in one place: allow for physical partition or replication

  3. Examples • Luxury hotel • Goal: Personalized attention to detail • Store customer preferences for repeat visits • When cleaning room, take note of pillows used, newspapers, drink bottles and snack wrappers discarded • Log requests, compliments, complaints • On next visit, provide complimentary item as token of recognition • Garage • Take note of odometer reading • Do they only come in for oil change? Give birthday discount on other service

  4. Not 1 database • A large company probably needs more than 1 database, each with its own purpose • Inventory control (materials, parts, finished goods) • Sales (customers and orders) • Manufacturing (production schedule, which factory) • Accounting (corporate taxes, dividends, payroll) • Within a database, could have several tables: • Example: Customer, Orders, Order Details, Product • Many-to-many relationship

  5. Views • view = subset of a database • Details not relevant to you are hidden • When you access a database, it is for a particular function (data entry, lookup). Each function has its own view. • Some information is confidential • Ex. Customer order history • Contact info not needed • Ex. Item order history • Customer info, quantity of item on hand not needed • This is why many queries are not “select * …”

  6. Database design factors • Storage cost, Also the need for backups (reliability) • Processing cost: Do we have a powerful enough server? • Communication cost: Bandwidth and ISP server cost • Retrieval and processing: how long should it take to get a confirmation • Making all information available to everyone in company may be impractical. • Find out what info people need most often • Frequency of updates and queries • How often the store should send records to HQ

  7. Concurrency • Allowing several people to access database at same time • Example: • Suppose there’s 1 seat left on tomorrow’s flight 17. • Customers A and B simultaneously query availability for that flight. • A buys a ticket. • B’s screen still shows 1 seat available. B also buys a ticket. • Problem is that the purchase is not instantaneous, and 2 transactions can overlap. • Possible solution: record locking • Each seat on flight is a record in some table. • B cannot purchase seat, because A has already begun process of selecting and buying ticket.

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