Column Data

The cursor library creates a buffer in the cache for each data buffer bound to the result set with SQLBindCol. It uses the values in these buffers to construct a WHERE clause when it emulates a positioned update or delete statement. It updates these buffers from the rowset buffers when it fetches data from the data source and when it executes positioned update statements.

When the cursor library updates its cache from the rowset buffers, it transfers the data according to the C data type specified in SQLBindCol. For example, if the C data type of a rowset buffer is SQL_C_SLONG, the cursor library transfers four bytes of data; if it is SQL_C_CHAR and BufferLength is 10, the cursor library transfers 10 bytes of data. The cursor library does not perform any type checking or conversions on the data it transfers.

Note The cursor library does not update its cache for a column if *StrLen_or_IndPtr in the corresponding rowset buffer is SQL_DATA_AT_EXEC or the result of the SQL_LEN_DATA_AT_EXEC macro.

When it updates a column, a data source blank-pads fixed-length character data and zero-pads fixed-length binary data as necessary. For example, a data source stores “Smith” in a CHAR(10) column as “Smith ”. The cursor library does not blank- or zero-pad data in the rowset buffers when it copies this data to its cache after executing a positioned update statement. Therefore, if an application requires that the values in the cursor library’s cache are blank- or zero-padded, it must blank- or zero-pad the values in the rowset buffers before executing a positioned update statement.