The DropDownDataWindow edit style
Sometimes another data source determines which data is valid
for a column.
Consider this situation: the Department table
includes two columns, Dept_id and Dept_name,
to record your company’s departments. The Employee table records
your employees. The Department column in the Employee table
can have any of the values in the Dept_id column
in the Department table.
As new departments are added to your company, you want the DataWindow object containing
the Employee table to automatically provide
the new departments as choices when users enter values in the Department column.
In situations such as these, you can specify the DropDownDataWindow
edit style for a column: it is populated from another DataWindow object.
When users go to the column, the contents of the DropDownDataWindow
display, showing the latest data:
To use the DropDownDataWindow edit style:
-
Create a DataWindow object that contains the columns
in the detail band whose values you want to use in the column.You will often choose at least two columns: one column that
contains values that the user sees and another column that contains
values to be stored in the database. In the example above, you would
create a DataWindow object containing the dept_id and dept_name columns
in the Department table. Assume this DataWindow object is
named d_dddw_dept. -
For the column in a second DataWindow getting its data
from the d_dddw_dept DataWindow object,
select the DropDownDW edit style.In the example, you would specify the DropDownDataWindow edit
style for the dept_id column that
you want to display with the department name as well as the department
ID:
-
Click the browse button next to the DataWindow box and
select the DataWindow object that contains the data for the column from
the list (in the example, d_dddw_dept).
The list includes all the DataWindow objects in the current target. -
In the Display Column box, select the column containing
the values that will display in the DataWindow object (in the example, dept_name). -
In the Data Column box, select the column containing
the values that will be stored in the database (in the example, dept_id). -
Specify other properties for the edit style.
What happens
At runtime, when data is retrieved into the DataWindow object, the
column whose edit style is DropDownDataWindow will itself be populated
as data is retrieved into the DataWindow object serving as the drop-down DataWindow object.
When the user goes to the column and drops it down, the contents
of the drop–down DataWindow object display. When the user selects
a display value, the corresponding data value is stored in the DataWindow
buffer and is stored in the database when an Update is
issued.
Limit on size of data value
The data value for a column that uses the DropDownDataWindow
edit style is limited to 511 characters.