How to: Set Cursor Options (ODBC)
New: 14 April 2006
To set cursor options, Call SQLSetStmtAttr to set or SQLGetStmtAttr to get the statement options that control cursor behavior.
| Attribute | Specifies |
|---|---|
SQL_ATTR_CURSOR_TYPE |
Cursor type of forward-only, static, dynamic, or keyset-driven |
SQL_ATTR_CONCURRENCY |
Concurrency control option of read-only, locking, optimistic using timestamps, or optimistic using values |
SQL_ATTR_ROW_ARRAY_SIZE |
Number of rows retrieved in each fetch |
SQL_ATTR_CURSOR_SENSITIVITY |
Cursor that does or does not show updates to cursor rows made by other connections |
SQL_ATTR_CURSOR_SCROLLABLE |
Cursor that can be scrolled forward and backward |
The default values for these attributes (forward-only, read-only, rowset size of 1) do not use server cursors. To use server cursors, at least one of these attributes must be set to a value other than the default, and the statement being executed must be a single SELECT statement or a stored procedure that contains a single SELECT statement. When using server cursors, SELECT statements cannot use clauses not supported by server cursors: COMPUTE, COMPUTE BY, FOR BROWSE, and INTO.
You can control the type of cursor used either by setting SQL_ATTR_CURSOR_TYPE and SQL_ATTR_CONCURRENCY, or by setting SQL_ATTR_CURSOR_SENSITIVITY and SQL_ATTR_CURSOR_SCROLLABLE. You should not mix the two methods of specifying cursor behavior.
Example
The following sample allocates a statement handle, sets a dynamic cursor type with row versioning optimistic concurrency, and then executes a SELECT.
retcode = SQLAllocHandle(SQL_HANDLE_STMT, hdbc1, &hstmt1);
retcode = SQLSetStmtAttr(hstmt1, SQL_ATTR_CURSOR_TYPE, (SQLPOINTER)SQL_CURSOR_DYNAMIC, _IS_INTEGER);
retcode = SQLSetStmtAttr(hstmt1, SQL_ATTR_CONCURRENCY, SQLPOINTER)SQL_CONCUR_ROWVER, _IS_INTEGER);
retcode = SQLExecDirect(hstmt1, SELECT au_lname FROM authors", SQL_NTS);
The following sample allocates a statement handle, sets a scrollable, sensitive cursor, and then executes a SELECT
retcode = SQLAllocHandle(SQL_HANDLE_STMT, hdbc1, &hstmt1);
// Set the cursor options and execute the statement.
retcode = SQLSetStmtAttr(hstmt1, SQL_ATTR_CURSOR_SCROLLABLE, SQLPOINTER)SQL_SCROLLABLE, _IS_INTEGER);
retcode = SQLSetStmtAttr(hstmt1, SQL_ATTR_CURSOR_SENSITIVITY, SQLPOINTER)SQL_INSENSITIVE, _IS_INTEGER);
retcode = SQLExecDirect(hstmt1, select au_lname from authors", SQL_NTS);
See Also
Other Resources
Executing Queries (ODBC) (How to)