PL/SQL Cursor常见用法模板

最新推荐文章于 2024-10-16 09:34:50 发布

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最新推荐文章于 2024-10-16 09:34:50 发布

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本文介绍PL/SQL中不同类型的循环结构及其使用方法，包括基本的LOOP循环、FOR循环以及利用BULK COLLECT进行数据批量处理的技术。通过实例展示了如何遍历游标并处理查询结果。

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1.Loop

DECLARE
   emp_rec emp%rowtype;

   CURSOR emp_cur IS
   SELECT *
   FROM emp;

BEGIN
   OPEN emp_cur;
   
   LOOP  
     FETCH emp_cur INTO emp_rec;
     EXIT WHEN emp_cur%NOTFOUND;--这个必须有,否则buffer overflow
     dbms_output.put_line (emp_rec.ename || '  ' ||emp_rec.sal );    
   END LOOP;

   CLOSE emp_cur;
END;

注：emp_rec必须和emp_cur保持结构一致

2.For Loop

DECLARE
 
 CURSOR emp_cur IS
 SELECT * FROM emp;

BEGIN

 FOR emp_rec in emp_cur LOOP  

   dbms_output.put_line(emp_rec.empno || ' ' ||emp_rec.ename || ' ' ||emp_rec.sal);  

 END LOOP;

END;

对于FOR LOOP，无需声明一个record或者一个变量来存储Cursor的值，并且无需显示的Open,Fetch,Close游标

3.For Loop

DECLARE 

BEGIN 

 FOR emp_rec in (SELECT * FROM emp) LOOP  

 dbms_output.put_line( emp_rec.empno || ' ' ||emp_rec.ename || ' ' ||emp_rec.sal);  

 END LOOP; 

END;

4.FETCH cursor BULK COLLECT INTO a collection

DECLARE
   TYPE NameList IS TABLE OF emp.ename%TYPE;
   TYPE SalList IS TABLE OF emp.sal%TYPE;

   names NameList;
   sals SalList;

   CURSOR c1 IS SELECT ename,sal FROM emp WHERE job = 'CLERK';

   l_index NUMBER;
BEGIN
   OPEN c1;

   FETCH c1 BULK COLLECT INTO names,sals;
   
   l_index := names.FIRST;
   LOOP
     EXIT WHEN l_index IS NULL;

     dbms_output.put_line(names(l_index)||','||sals(l_index));

     EXIT WHEN l_index = names.LAST;
     l_index := names.NEXT(l_index);

   END LOOP;

   CLOSE c1;
END;

The BULK COLLECT clause lets you fetch entire columns from the result set, or the entire result set at once.