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Spreadsheets and Databases

Spreadsheets and Databases. Class 8 LBSC 690 Information Technology. Agenda. Questions Spreadsheets Database design. What’s a Spreadsheet?. Large table containing numbers May also contain labels to aid interpretation Columns are named with LETTERS Rows are named with NUMBERS

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Spreadsheets and Databases

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  1. Spreadsheets andDatabases Class 8 LBSC 690 Information Technology

  2. Agenda • Questions • Spreadsheets • Database design

  3. What’s a Spreadsheet? • Large table containing numbers • May also contain labels to aid interpretation • Columns are named with LETTERS • Rows are named with NUMBERS • Cells are named like A4, C1, ... • Some cells are automatically calculated • Formula specified when spreadsheet is created • Values are recalculated continuously

  4. How Spreadsheets are Used • Record keeping (cassette tapes) • Calculation (income tax) • What-if analysis (cash flow) • Sensitivity analysis (exchange rate) • Goal seeking (retirement planning) • Uses continuous recalculation (“iteration”)

  5. How Spreadsheets are Used • Record keeping (cassette tapes) • Calculation (income tax) • What-if analysis (cash flow) • Sensitivity analysis (exchange rate) • Goal seeking (retirement planning) • Uses continuous recalculation (“iteration”)

  6. Spreadsheet Applications • Originally designed for financial records • Library applications • Budget • Collection development • Shelving capacity • Educational Applications • Grade records • Equipment inventory

  7. Excel Demo • Start Excel • Microsoft Office folder • Open N:\SHARE\CLASS\POSTCARD.XLS • File menu • Enter your 1997 (desired) income in cell B3 • Tax due is displayed in cell B4

  8. Excel Demo • Change the tax due • Place the cursor over B4 • Type “=B3*0.x” • “=” tells Excel this is a formula • “B3” refers to the number in cell B3 • The “x” in “0.x” should reflect your political views • 0.5 would take away half your money • Try different values in cell C3 • What kind of spreadsheet use is this?

  9. Excel Demo • Add itemized deductions • Highlight row 4 (click on 4) • Select “Row” in “Insert” menu twice • Label A4 as “Deduction amount” • Label A5 as “Taxable income” • Put the appropriate formula in B5 • Change the formula in B6 as needed • Note how it was copied from B4 with changes

  10. Excel Demo • Limit the deduction • Maximum of 50% of income or 10,000 • Search for help on “maximum” • Replace the formula in B5 with a more complicated one • You can use another cell to show a partial result

  11. When Style is Important • Too complex to visualize at once • Size • Relationships between formulas • Used by more than one person • Includes use in presentations and papers • Used for a long time • Essentially communicating to yourself

  12. Style Guidelines • Organization • Depict the solution approach visually • Group things where possible (e.g., parameters) • Build in cross-checks to discover input errors • Readability • Describe the computation • Meaningful labels help a lot • Minimize clutter

  13. Building Complex Applications • Computers keep track of detail well • But people don’t • Adopt meaningful abstractions • Organize a calculation the way you think • Use a structured process • Examples: waterfall and spiral models

  14. Relational Databases • Tables represent relations • Name, project • Name, email address, phone number • Relations can be “joined” • Name, project, email address, phone number • Relations can be “projected” • Name, email address • Relations can be “restricted” • Name = “Doug Oard”

  15. Why use Join? • Forces consistency • Doug Oard, project 18, oard@glue, 57590 • Doug Oard, project 22, oard@wam, 57590 • Limits the chance of error • Doug Oard, project 18, oard@glue, 57590 • Doug Oard, project 19, oard@glue, 57490 • Avoids lots of duplicated entry and updates • Can save a lot of storage space

  16. Problems with Joins • Data modeling for joins is complex • Taught in LBSC 670 • Joins are expensive to compute • Both in time and storage space • But it is joins that make databases relational • Projection and restriction also used in flat files

  17. Key Fields • Primary Key uniquely identifies line to join • May group several fields to get a unique key • Social security number • First and last name • “Foreign” key must appear in the other table • But it need not be unique there • Join makes a new table • Line specified by foreign key is tacked on

  18. Example of a Join on “Team” Team Team Name Team Project Name Project Chris A A Database Chris A Database Chris A B Web Chris A Database Camile A C Web Camile A Database Eileen B Eileen B Web Natalie C Natalie C Web David B David B Web Tonya C Tonya C Web Michelle Michelle Skip C Skip C Web

  19. Project to Keep Two Fields Team Team Name Project Name Project Chris A A Database Chris Database Chris A B Web Chris Database Camile A C Web Camile Database Eileen B Eileen Web Natalie C Natalie Web David B David Web Tonya C Tonya Web Michelle Michelle Skip C Skip Web

  20. Restrict to Web Pages Team Team Name Project Name Project Chris A A Database Eileen Web Chris A B Web Natalie Web Camile A C Web David Web Eileen B Tonya Web Natalie C Skip Web David B Tonya C Michelle Skip C

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