Adding summary statistics
One of the advantages of creating a grouped DataWindow object is
that you can have PowerBuilder calculate statistics for each group.
To do that, you place computed fields that reference the group.
Typically, you place these computed fields in the group’s
trailer band.
To add a summary statistic:
-
Select Insert>Control>Computed
Field from the menu bar. -
Click in the Design view where you want the statistic.
The Modify Expression dialog box displays.
-
Specify the expression that defines the computed
field (see below). -
Click OK.
A shortcut to sum values
If you want to sum a numeric column, select the column in
Design view and click the Sum button in the Controls drop-down toolbar. PowerBuilder automatically
places a computed field in the appropriate band.
Specifying the expression
Typically, you use aggregate and other functions in your summary
statistic. PowerBuilder lists functions you can use in the Functions
box in the Modify Expression dialog box. When you are defining a
computed field in a group header or trailer band, PowerBuilder automatically
lists forms of the functions that reference the group:
You can paste these templates into the expression, then replace
the #x that is pasted in as the function argument with
the appropriate column or expression.
For example, to count the employees in each department (group
1), specify this expression in the group trailer band:
|
1 |
Count( Emp_Id for group 1 ) |
To get the average salary of employees in a department, specify:
|
1 |
Avg( Salary for group 1 ) |
To get the total salary of employees in a department, specify:
|
1 |
Sum( Salary for group 1 ) |
The group trailer band in this example shows the average and
total salary for the group.
At runtime, the average and total salaries are calculated
and displayed:
