CS 111 – Nov. 19

1. 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

2. 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 * …”

3. 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

4. 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.

5. 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.

6. 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

7. 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?