The ODBC Driver uses a cursor concept to keep track of its position in the resultset, that is, in the data rows retrieved from the database. A cursor is used for tracking and indicating the current position, as the cursor on a computer screen indicates current position.
Each time an application calls SQLFetch, the driver moves the cursor to the next row and returns that row. An application can also call SQLFetchScroll or SQLExtendedFetch (ODBC 2.x), which fetches more than one row with a single fetch or call into the application buffer. This is known as “block cursor” support. Note that the actual number of rows fetched depends upon the rowset size specified by the application.
An application can call SQLSetPos to position a cursor within a fetched block of data using the SQL_POSITION option. This allows an application to refresh data in the rowset. SQLSetPos is also called to update data with the SQL_UPDATE option or delete data in the resultset with the SQL_DELETE option.
The cursor supported by the core ODBC functions only scrolls forward, one row at a time. (To re-retrieve a row of data that it has already retrieved from the resultset, the application must close the cursor by calling SQLFreeStmt with the SQL_CLOSE option, re-execute the SELECT statement, and fetch rows with SQLFetch, SQLFetch Scroll, or SQLExtendedFetch (ODBC 2.x) until the target row is retrieved.) If you need the ability to scroll backward as well as forward, use block cursors.