☰ Contents · Computing

Tables and relationships

Lessons 26–27 · 2 lessons · N. I. Taylaqov (general editor), A. B. Akhmedov, M. D. Pardayeva, A. A. Abdug‘aniyev, U. M. Mirsanov. Informatics and Information Technologies, Grade 10, 1st edition. “Extremum-Press”, Tashkent, 2017
26

Practical lesson

Textbook: p. 56
GoalCreates several tables in Access and uses the Totals row to find the sum, mean, largest, smallest and count of a column.
New words
Totals row: an extra row under a table that calculates one value for a column · Totals qatoriSum: the total of all values in a column · SumAverage: the arithmetic mean of a column · AverageCount: how many records have a value in the column · Count
Explanation

In the practical lesson you create a table with Create – Table (Datasheet view) or Create – Table Design, give each field a suitable type and enter data. To calculate on a numeric field, open the table in Datasheet View and press the Σ Totals button on the Home tab: a “Total” row appears under the table. Click the cell of that row in the column you need and choose Sum, Average, Count, Maximum or Minimum from the list. The result shows at once in the cell and updates when the table changes. The Totals row only displays: it does not change the records or add a new record. Making several independent tables prepares you to link them in the next lesson.

Worked examples
A “Routes” table: Name and LengthKm. The lengths are 12, 8, 15, 20, 10 km. In the Totals row Sum = 65, Average = 13, Maximum = 20, Minimum = 8, Count = 5. Check: (12+8+15+20+10)/5 = 13.
Three tables: “Clubs” (ClubID, ClubName), “Students” (StudentID, FullName, ClubID) and “Marks” (StudentID, Informatics). They are not linked yet; each is saved under its own name. If the marks are 4, 5, 3, 5, the Totals Average = 4.25.
Class activity

“The calculation master”: each student makes a table with 5 invented numbers, gets five results in the Totals row and compares them with the matching Excel formulas.

Practice
1
Which tab holds the Totals button?
2
A table holds the numbers 6, 9, 12, 5. What is Sum in the Totals row?
3
For the same numbers, write Maximum and Minimum.
4
Why does the Totals row not increase the number of records?