Call Level Interface Guide and Reference

Column Binding Offsets

When an application needs to change bindings (for a subsequent fetch for example) it can call SQLBindCol() a second time. This will change the buffer address and length/indicator pointer used.

Instead of multiple calls to SQLBindCol(), DB2 CLI also supports column binding offsets. Rather than re-binding each time, an offset can be used to specify new buffer and length/indicator addresses which will be used in a subsequent call to SQLFetch() or SQLFetchScroll(). This can only be used with row wise binding, but will work whether the application retrieves a single row or multiple rows at a time.

To make use of column binding offsets, an application would follow these steps:

1. Call SQLBindCol() as usual. The first set of bound data buffer and length/indicator buffer addresses will act as a template. The application will then move this template to different memory locations using the offset.

2. Call SQLFetch() or SQLFetchScroll() as usual. The data returned will be stored in the locations bound above.

3. Set up a variable to hold the memory offset value.

   The statement attribute SQL_ATTR_ROW_BIND_OFFSET_PTR points to the address of an SQLINTEGER buffer where the offset will be stored. This address must remain valid until the cursor is closed.

   This extra level of indirection enables the use of a single memory variable to store the offset for multiple sets of bindings on different statement handles. The application need only set this one memory variable and all of the offsets will be changed.

4. Store an offset value (number of bytes) in the memory location pointed to by the statement attribute set in the previous step.

   The offset value is always added to the memory location of the originally bound values. This sum must point to a valid memory address.

5. Call SQLFetch() or SQLFetchScroll() again. CLI will add the offset specified above to the locations used in the original call to SQLBindCol() to determine where in memory to store the results.

6. Repeat steps 4 and 5 above as required.

See the section Column Binding Offsets in SQLBindCol() for more information.

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