db_custom_field_rel

ColumnTypeReferencesComments
idInteger Primary key
vdb_idInteger  
custom_field_def_idIntegerdb_custom_field_def.id 
object_idInteger The id of the object_type to which this custom field is attached. Null indicates all objects of object_type.
object_typeInteger The object to which this custom field is attached. e.g Project, Task, Process Type etc.