(转)Oraclepl/sql中实现continue的步骤

(转)Oraclepl/sql中实现continue的方法
3611人阅读?评论(0)?CREATE?TABLE?AREAS
(
??RADIUS??NUMBER(5),
??AREA????NUMBER(14,2)
);

方法一：使用 goto

DECLARE
???pi???CONSTANT?NUMBER?(9,?7)??:=?3.1415927;
???radius????????INTEGER?(5);
???area??????????NUMBER?(14,?2);
BEGIN
???radius?:=?0;

???LOOP

??????<<here>>
??????radius?:=?radius?+?1;

??????IF?radius?=?4
??????THEN
?????????GOTO?here;
??????ELSE
?????????area?:=?pi?*?POWER?(radius,?2);

?????????INSERT?INTO?areas
??????????????VALUES?(radius,?area);

?????????EXIT?WHEN?area?>?100;
??????END?IF;
???END?LOOP;

???COMMIT;
EXCEPTION
???WHEN?OTHERS
???THEN
??????ROLLBACK;
??????RAISE;
END;

?-- 方法二：使用 exception

--?利用系统?exception
DECLARE
???pi?????CONSTANT?NUMBER?(9,?7)??:=?3.1415927;
???radius??????????INTEGER?(5);
???area????????????NUMBER?(14,?2);
???some_variable???NUMBER?(14,?2);
BEGIN
???radius?:=?0;

???LOOP
??????BEGIN
?????????radius?:=?radius?+?1;
?????????some_variable?:=?1?/?(radius?-?4);
?????????area?:=?pi?*?POWER?(radius,?2);

?????????INSERT?INTO?areas
??????????????VALUES?(radius,?area);

?????????EXIT?WHEN?area?>?100;
??????EXCEPTION
?????????WHEN?ZERO_DIVIDE
?????????THEN
????????????NULL;
??????END;
???END?LOOP;

???COMMIT;
EXCEPTION
???WHEN?OTHERS
???THEN
??????ROLLBACK;
??????RAISE;
END;

?

--?自定义?exception
DECLARE
???pi??????????????CONSTANT?NUMBER?(9,?7)??:=?3.1415927;
???radius???????????????????INTEGER?(5);
???area?????????????????????NUMBER?(14,?2);
???e_userdefinedexception???EXCEPTION;
???PRAGMA?EXCEPTION_INIT?(e_userdefinedexception,?-1401);
BEGIN
???radius?:=?0;

???LOOP
??????radius?:=?radius?+?1;

??????BEGIN
?????????IF?radius?=?4
?????????THEN
????????????RAISE?e_userdefinedexception;
?????????ELSE
????????????area?:=?pi?*?POWER?(radius,?2);

????????????INSERT?INTO?areas
?????????????????VALUES?(radius,?area);

????????????EXIT?WHEN?area?>?100;
?????????END?IF;
??????EXCEPTION
?????????WHEN?e_userdefinedexception
?????????THEN
????????????NULL;
??????END;
???END?LOOP;

???COMMIT;
EXCEPTION
???WHEN?OTHERS
???THEN
??????ROLLBACK;
??????RAISE;
END;转自：http://www.itpub.net/thread-1118901-1-1.html如果CONTINUE只有一两处，而且可以轻易变成IF..ELSE.., 那么就用IF ELSE, 这也是TOM推荐的方法。
但有时候CONTINUE藏在其他复杂的控制结构里面，IF ELSE 就不容易搞定了。我会用这种方法：


FOR 或者 WHILE 主循环 LOOP
? ? FOR v_foo IN 1..1 LOOP? ???---- 第二层假循环

? ?? ???……代码……
? ?? ???IF …… THEN
? ?? ?? ???EXIT;? ?? ?---- 退出假循环，等效于CONTINUE主循环
? ?? ???END IF;
? ?? ???……代码……
? ?? ??
? ?? ???IF …… THEN?
? ?? ?? ???EXIT main_loop;? ? ---- 如果需要退出主循环，用这个写法
? ?? ???END IF;

? ?? ???……代码……

? ? END LOOP v_foo;??---- 第二层假循环结束
END LOOP main_loop; ---- 主循环结束

初看有些古怪，因为用EXIT代替了CONTINUE. 但习惯了就会发现很灵活。

查看更多 下一篇