aspect-queries.md

Querying for Aspects of an Element

This section uses the iModel Console to execute queries against the Stadium sample iModel.

Open an iModel in the iModel Console

1. Go to https://imodelconsole.bentley.com
2. Select the project, then select an iModel then select a changeset
3. Wait until the green button in the lower right says Run

Identifying the Aspects applied to an Element

There are two types of aspect, unique and multi. They are stored in independent tables and must be queried for independently.

1. Query for aspects in the iModel

   SELECT * FROM bis.ElementMultiAspect

   SELECT * FROM bis.ElementUniqueAspect

   NOTE: The base aspect classes only have one property, Element it is a navigation property that points to the Element that owns the Aspect

2. Query for aspects and the elements that own them

   SELECT * FROM bis.ElementMultiAspect a JOIN bis.Element e ON e.ECInstanceId = a.Element.Id

3. Query for Element classes and the aspect classes applied to them

   SELECT ec_classname(e.ECClassId) Element_Class, json_group_array(DISTINCT(ec_className(a.ECClassId))) Aspect_Classes FROM bis.Element e 
       JOIN bis.ElementMultiAspect a ON a.Element.Id = e.ECInstanceId
       GROUP BY e.ECClassId

   Queries like this that look for distinct classes are helpful when trying to determine the nature of the data in an iModel. Notice that Generic.PhysicalObject has the most aspect classes.

4. Query for a specific Element and its aspects. This query uses the element selected by clicking on a glass section in the stadium.

   SELECT * FROM bis.Element e JOIN bis.ElementMultiAspect a ON a.Element.Id = e.ECInstanceId WHERE e.ECInstanceId = 0x200000063de

5. Specialize query to get all properties

   SELECT * FROM Generic.PhysicalObject e JOIN DgnCustomItemTypes_SS_Steel_Structure.GlassElementAspect a ON a.Element.Id = e.ECInstanceId JOIN bis.ExternalSourceAspect a2 ON a2.Element.Id = e.ECInstanceId WHERE e.ECInstanceId = 0x200000063de

   Compare the properties selected to what is shown in Design Review.

Next: Spatial Queries