MDAC 2.5 SDK - OLE DB Programmer's Reference
Appendix C: OLE DB Properties

DBPROP_INDEX_NULLS

Property group: Index

Property set: DBPROPSET_INDEX

Type: VT_I4

Typical R/W: R/W

Description: NULL Keys

Indicates whether NULL keys are allowed. One of the following values:

• DBPROPVAL_IN_DISALLOWNULL—The index does not allow entries where the key columns are NULL. If the consumer attempts to insert an index entry with a NULL key, the provider returns an error.
  
  
• DBPROPVAL_IN_IGNORENULL—The index does not insert entries containing NULL keys. If the consumer attempts to insert an index entry with a NULL key, the provider ignores that entry and no error code is returned.
  
  
• DBPROPVAL_IN_IGNOREANYNULL—The index does not insert entries where some column key has a NULL value. For an index having a multicolumn search key, if the consumer inserts an index entry with NULL value in some column of the search key, the provider ignores that entry and no error code is returned.
  
  
• DBPROPVAL_IN_ALLOWNULL—The index allows entries where the key columns are NULL and sorts according to the collation described by DBPROP_INDEX_NULLCOLLATION.