Dim objRe As New ADODB.Recordset
objRe.Open "select fld from tbl", , , adLockPessimistic
objRe.Open "select fld from tbl", , , adLockPessimistic
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-- Number of credits to add to each student's total
v_NumCredits classes.num_credits%TYPE; -- This cursor will select only those students who are currently
-- registered for HIS 101.
CURSOR c_RegisteredStudents IS
SELECT *
FROM students
WHERE id IN (SELECT student_id
FROM registered_students
WHERE department= 'HIS'
AND course = 101)
FOR UPDATE OF current_credits;BEGIN
-- Set up the cursor fetch loop.
FOR v_StudentInfo IN c_RegisteredStudents LOOP
-- Determine the number of credits for HIS 101.
SELECT num_credits
INTO v_NumCredits
FROM classes
WHERE department = 'HIS'
AND course = 101; -- Update the row we just retrieved from the cursor.
UPDATE students
SET current_credits = current_credits + v_NumCredits
WHERE CURRENT OF c_RegisteredStudents;
END LOOP; -- Commit our work, and release the lock.
COMMIT;
END;
/注意:在commit前,把所有dml语句操作,遇到事务处理就马上释放任何锁