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Three standard bookmark values are provided: DBBMK_INVALID, DBBMK_FIRST, and DBBMK_LAST. All single-byte (length 1) bookmark values of type DBTYPE_BYTES are reserved for standard bookmarks. Ordinary bookmarks of type DBTYPE_BYTES must be at least length 2. The following constant is defined in Oledb.h as the standard bookmark length:
#define STD_BOOKMARKLENGTH 1
The values of the standard bookmarks listed in the following table are guaranteed to be the same for all providers.
Value |
Meaning |
|---|---|
DBBMK_INVALID |
DBBMK_INVALID can be used by applications to initialize and subsequently check bookmark validity. |
DBBMK_FIRST |
The first row of the rowset. A consumer can fetch forward from this point. For example, if cRows is greater than zero and lRowsOffset is zero, IRowsetLocate::GetRowsAt returns the first cRows rows of the rowset. A consumer cannot fetch backward before this point. For example, if cRows is -1 and lRowsOffset is zero, IRowsetLocate::GetRowsAt returns this row. If cRows is less than ?1, it returns DB_S_ENDOFROWSET. |
DBBMK_LAST |
The last row of the rowset. If the rowset is being populated asynchronously, this is the last row identified so far. A consumer can fetch backward from this point. For example, if cRows is less than zero and lRowsOffset is zero, IRowsetLocate::GetRowsAt returns the last cRows rows of the rowset. A consumer cannot fetch forward past this point. For example, if cRows is one and lRowsOffset is zero, IRowsetLocate::GetRowsAt returns this row. If cRows is greater than one, it returns DB_S_ENDOFROWSET. |
The consumer can begin a sequential scan at either the first or last row.