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CS 111 – Nov. 19. Enterprise databases, continued Review tables, joins, queries Restricting one’s view of entire database Design considerations Concurrency Beyond the database Other systems you might see in business. Commitment Please read sections 7.1 – 7.3 Homework #2 due Nov. 29.
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CS 111 – Nov. 19 • Enterprise databases, continued • Review tables, joins, queries • Restricting one’s view of entire database • Design considerations • Concurrency • Beyond the database • Other systems you might see in business. • Commitment • Please read sections 7.1 – 7.3 • Homework #2 due Nov. 29
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 * …”
Database design factors • Storage cost, Also the need for backups (reliability) • Processing cost: • Do we have a powerful enough server? • Are database operations implemented efficiently? • Communication cost: Bandwidth and ISP server cost • Retrieval and processing: confirmation response time • 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
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 (especially major purchase) • 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.
Beyond database • We need data in IT (e.g. kept in a database), but that is not enough! • Transaction processing systems • Add record to “order” table • Support queries and summary reports • Automatic reporting of suspicious transactions (mistake, fraud?) • Management info systems • Provide information to make decisions: • How much merchandise to order? How many people to hire? Cheapest way to do ___ • These problems require general problem solving skill • Other similar “support systems” also exist for specialized purposes.
Big IT tasks • To make IT work, people are more important than HW or SW. Here are some examples. • Database administrators • Deal with database design, performance, security • Systems analysts • Analyze large problems (e.g. some IT service for company) • Estimate time & personnel needed to get jobs done • design large applications; may write mock-up prototype • draw up precise I/O and performance specifications • Project managers • Deal with day-to-day responsibilities • Maintain implementation schedule, with deliverables • Software engineers
Sample IT questions Feel free to paraphrase… Plus: Answers to one question may prompt you to ask a follow-up question. • What does IT encompass at your company? • What % of your employees are mostly involved in IT? • What sort of tasks need to get done? • Do you have systems analysts at your company? What do they do? • What other IT occupations do you have? • What skills (technical & nontechnical) or traits are needed for people who work in IT? • Specific knowledge and conceptual understanding • What is a typical career path for someone in IT? • What is most rewarding aspect of working in IT? Most challenging?
