SQL implementation differences for the ST_Geometry type

There is little difference between the implementation of spatial SQL (ST_Geometry) implementation for Informix, DB2, Oracle, and PostgreSQL. Esri, a partner and codeveloper of extended spatial SQL within the IBM database management system (DBMS) products, worked in a cooperative environment to ensure that the standards dictated by the Open Geospatial Consortium (OGC) were applied to the fullest extent possible.

There are, however, three notable exceptions, none of which actually breach the OGC standards, but are minor implementation idiosyncrasies of the DBMSs themselves.