Executing Positioned Update and Delete Statements
1 Calls SQLSetPos to position the cursor on the row to be updated or deleted.
2 Constructs a positioned update or delete statement with the following syntax:
UPDATE table-name
DELETE FROM table-name WHERE CURRENT OF cursor-name
The easiest way to construct the SET clause in a positioned update statement is to use parameter markers for each
column to be updated and use SQLBindParameter to bind these to the rowset buffers for the row to be updated. In this case,
the C data type of the parameter will be the same as the C data type of the
rowset buffer.
3 Updates the rowset buffers for the current row if it will execute a positioned
update statement. After successfully executing a positioned update statement,
the cursor library copies the values from each column in the current row to its
cache.
Caution If the application does not correctly update the rowset buffers before
executing a positioned update statement, the data in the cache will be incorrect
after the statement is executed.
4 Executes the positioned update or delete statement using a different statement
than the statement associated with the cursor.
Caution The WHERE clause constructed by the cursor library to identify the current row can fail
to identify any rows, identify a different row, or identify more than one row.
For more information, see
All positioned update and delete statements require a cursor name. To specify
the cursor name, an application calls SQLSetCursorName before the cursor is opened. To use the cursor name generated by the driver,
an application calls SQLGetCursorName after the cursor is opened.
After the cursor library executes a positioned update or delete statement, the
status array, rowset buffers, and cache maintained by the cursor library
contain the values shown in the following table.
SET column-identifier = {expression | NULL}
[, column-identifier = {expression | NULL}]
WHERE CURRENT OF cursor-name
|
Statement used |
Value in row status array | Values in
rowset buffers | Values in
cache buffers |
Positioned update | SQL_ROW_UPDATED
| New values [1]
| New values [1]
|
| Positioned delete
| SQL_ROW_DELETED
| Old values
| Old values
|
[1] The application must update the values in the rowset buffers before executing the positioned update statement; after executing the positioned update statement, the cursor library copies the values in the rowset buffers to its cache. |
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