Advanced PowerBuilder

DropDown/Child DataWindows

A column in a DataWindow can have one of the six edit styles. We've looked at most of them and seen situations where each style can be applied, but one edit style that we haven't looked in detail is the DropDownDataWindow Edit Style. When using other edit styles, the information you supply is stored in the PowerBuilder library. For example, we have e_tran_type edit style that is of DropDownListBox edit style. This, e_tran_type is a PowerBuilder object and is stored in the PowerBuilder system tables in the connected database. This is fine for the static data, but if you want to use dynamic data, the best solution would be to use DropDownDataWindow edit style.

For example, when adding a new product to the product_master table, product_measuring_unit should exist in the units table. We can use a DropDownDataWindow to display the information in the units table and allow the user to select from the available options, rather than checking the existence in the units table by issuing an SQL statement.

For it, all we need to do is create a DataWindow for the units table, with SQL Select data source and tabular presentation style. We already created this DataWindow, d_units_dropdown. Open that DataWindow in the DataWindow painter. Observe that, we deleted everything from the header.

Now, we need to change the edit style of product_measuring_unit column in d_product_maint DataWindow. Open the d_product_maint DataWindow, and double-click on the product_measuring_unit column. Click on the Edit Style tab page.

Select DropDownDW for the edit style prompt, d_units_dropdown for the DataWindow prompt, unit_description for the Display column prompt and unit for the Data Column prompt. Selecting Always Show Arrow option would always display an arrow at the right side of the column in the DataWindow.

Now, if we preview d_product_maint DataWindow, you'll see that for the product_measuring_unit column, we have a DropDownDataWindow containing details from the units table. An user always sees the unit_description on the screen, but, PowerBuilder sends the value of the "Data Column", i.e., "unit" to the database. This edit style allows us to use dynamic and up-to-date data with descriptive options.

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