About Query by Example and Query Builder


Query by Example (QBE) and the Query Builder (QB) were designed at the Lawrence Berkeley Laboratory to simplify query construction in ACEDB and are part of the standard release. The Moulon server makes them available for databases using versions 2 and 3. They are not available for version 1 databases. The database version is always stated in the "about" file for each database.

Note: You need a World Wide Web browser that recognizes HTML forms to use QBE and QB.

The "query" link next each ACEDB database displays the AGIS Search Form. This form offers several different query methods, including QBE and QB.

Query by Example uses simple pattern matching on a form to select objects. For example, to find all publications with "Jones" as an author in AAtDB, first select the Paper class. The next screen is a Query Paper class form with field names and text-entry boxes. Enter Jones* in the Author box and click the "Search" button at the top of the form. This returns a list of publications.

Query Builder allows more complex queries. Using the same query as above, you will see something like this:

Find and select Paper items

where

Change the "item name" to "author" and "exists" to "begins with". Then enter "Jones" (don't include the quotes) into the text-entry box. Click the "Search" button at the top of the form and a list of publications will appear. Queries can be extended by adding additional fields and conditions.