Creating a solution > About choosing a field type > Defining summary fields
 
Defining summary fields
Use summary fields to calculate values such as subtotals, averages, and grand totals across multiple records. For example, a summary field can display the grand total of all sales in the month of May in a report.
Summary fields are associated with groups of records. The value in a summary field can change depending on where you place the field on a layout, how many records are in the found set, and whether the records are sorted.
Data in a summary field reflects records currently being browsed; either all the records or a group of found records. If you change a value in one of the fields on which the summary is based, or if you change the found set, FileMaker Pro recalculates the result in a summary field.
To define summary fields:
1. With the database open, choose File menu > Manage > Database.
2. In the Manage Database dialog box, click the Fields tab.
3. If your database contains more than one table, select the appropriate table from the Table list.
4. For Field Name, type a name for the field.
See About naming fields.
5. For Type, select Summary.
6. Click Create.
7. In the Options for Summary Field dialog box, select a summary type, then select the field you want to group data by.
 
Select this type of
summary calculation
To summarize values in a field in the found set of records by
Total of
Calculating the total of values in the field.
Average of
Calculating the average of values in the field.
Count of
Counting the number of records that contain a value for the field. For example, if a field contains 100 values (one value for each record), the result of the count is 100.
Minimum
Finding the lowest number, or earliest date, time, or timestamp for a field.
Maximum
Finding the highest number, or latest date, time, or timestamp for a field.
Standard Deviation of
Finding how widely the values in a field differ from each other. This option calculates the standard deviation from the mean of the values in a field.
Fraction of Total of
Calculating the ratio of the value in the field to the total of all the values in that field. (For example, find what fraction of total sales can be attributed to each salesperson.)
List of
Creating a return-delimited list of non-blank values in a field.
8. Select a summary option, if applicable, for the summary type.
 
For
Select
To
Total of
Running total
Show the cumulative total for the current and all previous records. To restart the running total for each sorted group, also select Restart summary for each sorted group and select the field upon which the sort will be restarted from the field list.
Average of
Weighted average. In the field list that appears, select the field that contains the weight factor.
Determine the average in one field based on a value in another field that is used as a weight factor.
Count of
Running count
Show the cumulative count of the current and all previous records. To restart the running count for each sorted group, also select Restart summary for each sorted group and select the field upon which the sort will be restarted from the field list.
Standard Deviation of
By population
Calculate population standard deviation.
Fraction of Total of
Subtotaled. In the field list that appears, select the field to group by.
Calculate a fraction of the total based only on a group of records.
9. If the field you are summarizing is a repeating field, you have the option to summarize the repetitions together or individually.
Select All together to calculate a single summary value for all repetitions in the field.
Select Individually to calculate a summary value for each repetition.
Note  You must format your summary field as a repeating field to display individual summary values. See Setting up the display of repeating fields.
10. Click OK, then continue defining fields or click OK.
Notes
Use the New Layout/Report assistant to quickly create a layout that summarizes data. See Creating a layout.
If you choose Fraction of Total of, you can specify a group field for Subtotaled. When you return to Browse mode, you must sort by the group field to calculate the value correctly.
The standard deviation formula is n-1 weighted, following the normal standard deviation.
You can't change data in a summary field manually, but you can copy it. You can also perform calculations with summary fields using the GetSummary function.
Related topics 
Creating and managing layouts and reports
Specifying formats for fields containing numbers