Oracle数据库---游标

--查询所有员工的员工号、姓名和职位的信息。
DECLARE
--定义游标
CURSOR emp_cursor IS SELECT empno,ename,job FROM emp;
v_empno emp.empno%TYPE;
v_ename emp.ename%TYPE;
v_job emp.job%TYPE;
BEGIN
--打开游标，执行查询
OPEN emp_cursor;
--提取数据
LOOP
FETCH emp_cursor INTO v_empno,v_ename,v_job;
DBMS_OUTPUT.PUT_LINE('员工号：'||v_empno||'，姓名：'||v_ename||',职位：'||v_job);
--什么时候能够退出循环？
--%FOUND,%NOTFOUND
EXIT WHEN emp_cursor%NOTFOUND;
END LOOP;
--关闭游标
CLOSE emp_cursor;
END;

--查询所有员工的员工号、姓名和职位的信息。
DECLARE
--定义游标
CURSOR emp_cursor IS SELECT empno,ename,job FROM emp;
v_empno emp.empno%TYPE;
v_ename emp.ename%TYPE;
v_job emp.job%TYPE;
BEGIN
--打开游标，执行查询
--OPEN emp_cursor;
--检测游标是否打开
IF emp_cursor%ISOPEN THEN
DBMS_OUTPUT.PUT_LINE('游标已经打开');
ELSE
DBMS_OUTPUT.PUT_LINE('游标没有打开');
END IF;

END;

--游标FOR循环
DECLARE
CURSOR emp_cursor IS SELECT empno,ename,job FROM emp;
BEGIN
FOR emp_record IN emp_cursor LOOP
DBMS_OUTPUT.PUT_LINE('员工号：'||emp_record.empno||',姓名：'||emp_record.ename||',职位：'||emp_record.job);
END LOOP;
END;

--游标FOR循环中引用子查询
BEGIN
FOR emp_record IN (SELECT empno,ename,job FROM emp) LOOP
DBMS_OUTPUT.PUT_LINE('员工号：'||emp_record.empno||',姓名：'||emp_record.ename||',职位：'||emp_record.job);
END LOOP;
END;

--参数游标
DECLARE
CURSOR emp_cursor(dno NUMBER) IS SELECT empno,ename,job FROM emp WHERE deptno = dno;
BEGIN
FOR emp_record IN emp_cursor(&no) LOOP
DBMS_OUTPUT.PUT_LINE('员工号：'||emp_record.empno||',姓名：'||emp_record.ename||',职位：'||emp_record.job);
END LOOP;
END;

--根据用户输入的员工号，更新指定员工的工资，比如工资涨100
--隐式游标
BEGIN
UPDATE empnew SET sal = sal + 100 WHERE empno = &no;
IF SQL%FOUND THEN
DBMS_OUTPUT.put_line('成功修改员工的工资');
COMMIT;
ELSE
DBMS_OUTPUT.put_line('修改员工工资失败!');
ROLLBACK;
END IF;
END;

SELECT * FROM empnew;

--按职工的职称涨工资，总裁涨1000元，经理涨500元，其他员工涨300元。
--1：用显示游标的常规方式实现业务需求
DECLARE
--定义游标
CURSOR empnew_cursor IS SELECT empno,job FROM empnew;
v_empno empnew.empno%TYPE;
v_job empnew.job%TYPE;
BEGIN
--打开游标
OPEN empnew_cursor;
--提取数据
LOOP
FETCH empnew_cursor INTO v_empno,v_job;
IF v_job='PRESIDENT' THEN
UPDATE empnew SET sal = sal + 1000 WHERE empno = v_empno;
ELSIF v_job='MANAGER' THEN
UPDATE empnew SET sal = sal + 500 WHERE empno = v_empno;
ELSE
UPDATE empnew SET sal = sal + 300 WHERE empno = v_empno;
END IF;
EXIT WHEN empnew_cursor%NOTFOUND;
END LOOP;
COMMIT;
--关闭游标
CLOSE empnew_cursor;
END;

--2：用游标FOR循环的方式实现业务需求
DECLARE
--定义游标
CURSOR empnew_cursor IS SELECT empno,job FROM empnew;
BEGIN
FOR empnew_record IN empnew_cursor LOOP
DBMS_OUTPUT.put_line(empnew_record.empno||'----'||empnew_record.job);
IF empnew_record.job = 'PRESIDENT' THEN
UPDATE empnew SET sal = sal + 1000 WHERE empno = empnew_record.empno;
ELSIF empnew_record.job = 'MANAGER' THEN
UPDATE empnew SET sal = sal + 500 WHERE empno = empnew_record.empno;
ELSE
UPDATE empnew SET sal = sal + 300 WHERE empno = empnew_record.empno;
END IF;
END LOOP;
--COMMIT;
END;

select * from empnew for update;

--3：使用游标添加或删除数据时，定义游标时利用FOR UPDATE 子句可以将游标提取出来的数据进行行级锁定
DECLARE
--定义游标
CURSOR empnew_cursor IS SELECT empno,job FROM empnew FOR UPDATE;
BEGIN
FOR empnew_record IN empnew_cursor LOOP
DBMS_OUTPUT.put_line(empnew_record.empno||'----'||empnew_record.job);
IF empnew_record.job = 'PRESIDENT' THEN
UPDATE empnew SET sal = sal + 1000 WHERE CURRENT OF empnew_cursor;
ELSIF empnew_record.job = 'MANAGER' THEN
UPDATE empnew SET sal = sal + 500 WHERE CURRENT OF empnew_cursor;
ELSE
UPDATE empnew SET sal = sal + 300 WHERE CURRENT OF empnew_cursor;
END IF;
END LOOP;
COMMIT;
END;

SELECT * FROM empnew;

--FOR UPDATE NOWAIT 不等待锁，如发现所操作的数据行已经锁定，将不会等待，立即返回
DECLARE
--定义游标
CURSOR empnew_cursor IS SELECT empno,job FROM empnew FOR UPDATE NOWAIT;
BEGIN
FOR empnew_record IN empnew_cursor LOOP
DBMS_OUTPUT.put_line(empnew_record.empno||'----'||empnew_record.job);
IF empnew_record.job = 'PRESIDENT' THEN
UPDATE empnew SET sal = sal + 1000 WHERE CURRENT OF empnew_cursor;
ELSIF empnew_record.job = 'MANAGER' THEN
UPDATE empnew SET sal = sal + 500 WHERE CURRENT OF empnew_cursor;
ELSE
UPDATE empnew SET sal = sal + 300 WHERE CURRENT OF empnew_cursor;
END IF;
END LOOP;
COMMIT;
END;

SELECT * FROM empnew;

--使用OF子句在特定表上加行共享锁
DECLARE
CURSOR empnew_cursor IS
SELECT d.dname dname,e.ename ename
FROM empnew e join dept d on e.deptno = d.deptno
WHERE e.deptno = &deptno
FOR UPDATE OF e.deptno;
BEGIN
FOR empnew_record IN empnew_cursor LOOP
DBMS_OUTPUT.PUT_LINE('部门名称：'||empnew_record.dname||'员工名：'||empnew_record.ename);
DELETE FROM empnew WHERE CURRENT OF empnew_cursor;
END LOOP;
COMMIT;
END;

SELECT * FROM empnew where deptno = 20;