DB2 Version 10.1 for Linux, UNIX, and Windows

Transform groups

Spatial Extender provides four transform groups that are used to transfer geometries between the DB2® server and a client application.

These transform groups accommodate the following data exchange formats:
  • Well-known text (WKT) representation
  • Well-known binary (WKB) representation
  • ESRI shape representation
  • Geography Markup Language (GML)

When data is retrieved from a table that contains a spatial column, the data from the spatial column is transformed to either a CLOB(2G) or a BLOB(2G) data type, depending on whether you indicated whether the transformed data was to be represented in binary or text format. You can also use the transform groups to transfer spatial data to the database.

To select which transform group is to be used when the data is transferred, use the SET CURRENT DEFAULT TRANSFORM GROUP statement to modify the DB2 special register CURRENT DEFAULT TRANSFORM GROUP. DB2 uses the value of this special register to determine which transform functions must be called to perform the necessary conversions.

Transform groups can simplify application programming. Instead of explicitly using conversion functions in the SQL statements, you can specify a transform group, which lets DB2 handle that task.