When you choose a query as the data source, you select a predefined SQL SELECT statement (a query) as specifying the data for your .
Queries save time, because you specify all the data requirements just once. For example, you can specify the columns, which rows to retrieve, and the sorting order in a query. Whenever you want to create a DataWindow object using that data, simply specify the query as the data source.
You can edit existing queries using the text editor.