Microsoft Access Tutorial B - Cengage Learning

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Figure B-35Output of query with date arithmeticUsing Time Arithmetic in QueriesAccess will also let you subtract the values of time fields to get an elapsed time. Assume thatyour database has a JOB ASSIGNMENTS table showing the times that non-salaried employeeswere at work during a day. The definition is shown in Figure B-36.Figure B-36Date/Time data definition in the JOB ASSIGNMENTS tableAssume that the Date field is formatted for Long Date and that the ClockIn andClockOut fields are formatted for Medium Time. Assume that, for a particular day, nonsalariedworkers were scheduled as shown in Figure B-37.Figure B-37Display of date and time in a tableYou want a query that will show the elapsed time on premises for the day. When youadd the tables, your screen may show the links differently. Click and drag the JOBASSIGNMENTS, EMPLOYEE, and WAGE DATA table icons to look like those inFigure B-38.30 Tutorial B
Tutorial BFigure B-38Query set-up for time arithmeticFigure B-39 shows the output.Figure B-39Query output for time arithmeticThe output looks right. For example, employee 099-11-3344 was at work from 8:30 a.m.to 4:30 p.m., which is eight hours. But how does the odd expression that follows yield thecorrect answers?([ClockOut] – [ClockIn]) * 24Why wouldn’t the following expression, alone, work?[ClockOut] – [ClockIn]This is the answer: In Access, subtracting one time from the other yields the decimalportion of a 24-hour day. Employee 099-11-3344 worked 8 hours, which is one-third of aday, so .3333 would result. That is why you must multiply by 24—to convert to an hourbasis. Continuing with 099-11-3344, 1/3 x 24 = 8.Note that parentheses are needed to force Access to do the subtraction first, before themultiplication. Without parentheses, multiplication takes precedence over subtraction. Withthe following expression, ClockIn would be multiplied by 24 and then that value would besubtracted from ClockOut, and the output would be a nonsense decimal number:[ClockOut] – [ClockIn] * 24Delete and Update QueriesThus far, the queries presented in this tutorial have been Select queries. They select certaindata from specific tables, based on a given criterion. You can also create queries to update theoriginal data in a database. Businesses do this often, and in real time. For example, when youMicrosoft Access Tutorial 31
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Page 6 and 7: show the SSN, the current wage rate
Page 8 and 9: • Spell, capitalize, and space a
Page 10 and 11: Figure B-17 Query set-up for wages
Page 12 and 13: Figure B-21Choices for statistical
Page 14 and 15: When you run the query, your output
Page 16 and 17: Figure B-31Changing the Group By to
Page 20 and 21: order an item from a Web site, the
Page 22 and 23: those records not in Delaware (DE).
Page 24 and 25: 1. Create a query that shows the SS
Page 26 and 27: FieldTableSortShowCriteriaOr:Figure
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Page 30 and 31: Figure B-65Sorting and Summary Opti
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Page 34 and 35: You can change the Grand Total in t
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Page 38 and 39: Find and import your spreadsheet. B
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Page 42 and 43: Make sure the Toolbox window is sho
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Page 46 and 47: TROUBLESHOOTING COMMON PROBLEMSAcce
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