Introduction to PowerBuilder

Filtering Data

If you have a large table with a million rows and want to see only rows that belong to a specific country, what you do? You put a WHERE clause in the SELECT statement to select only those rows that you want to see. However, when you open the pane to edit the data in the database painter, PowerBuilder brings all the data from that table, you don't have the option of specifying WHERE clause. Well, you can click on the Stop icon (Retrieve icon toggles to Stop icon while data is being retrieved) to stop retrieving the data, but you have no control to specify exactly where to stop. This is where PowerBuilder filter feature comes in. Using this feature, you can filter the data that is already retrieved into the client buffer (PowerBuilder). To filter data, select 'Rows > Filter...' menu option.

An expression can be built using any of the available functions from the list, fields in the table and a selection of mathematical operators. For example to display the rows with a description of six characters or less, we would use the following expression:

len( unit_description ) <= 6

Only those rows that pass the filter criteria are displayed. It doesn't mean that the rest of the data is gone, it is still available on the local machine and there are no changes made to the back-end database. Remove the filter and all the data will be displayed.

When you are in the Filter Expression dialog box, you can check your expression's syntax by clicking on the Verify button.

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