oracle 如果在循环 PL SQL 中满足条件，如何退出过程
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how to exit the procedure if condition met in a loop PL SQL
提问by dozel
Let's say I have a for loop
假设我有一个 for 循环
for i in array.first .. array.last loop
boolean := c(i) > d(i);
if boolean --is true then
exit the loop immediately and also exit the entire procedure
else if the boolean is never true til the end of the loop, exit the loop
and keep running other scripts in this procedure.
I know the 'EXIT' keyword needs to be inside of the loop in order to exit the loop if condition is met. And 'RETURN' needs to be outside of the loop, to exit the procedure.
我知道 'EXIT' 关键字需要在循环内才能在满足条件时退出循环。并且 'RETURN' 需要在循环之外，以退出该过程。
But if I put 'RETURN' outside of the loop, then I think no matter what the result is from the loop, it will exit the entire procedure when the loop ends?
但是如果我把'RETURN'放在循环之外，那么我认为无论循环的结果是什么，循环结束时它都会退出整个过程？
回答by Bob Jarvis - Reinstate Monica
If you want to be didactic about it, you should use an EXIT to get out of the loop, then use a RETURN to exit from the procedure (duplicating any necessary tests), thus following the structured programming rule that "A procedure should only have a single entrance and a single exit". In practice 99.999% of programmers would just code the RETURN inside the body of the loop because A) it's clearer as to what's going on (you're not just getting out of the loop, you're returning from the procedure), and B) it's shorter. Do as you will. Best of luck.
如果你想说教，你应该使用 EXIT 退出循环，然后使用 RETURN 退出过程（复制任何必要的测试），从而遵循结构化编程规则“一个过程应该只有一个入口和一个出口”。在实践中，99.999% 的程序员只会在循环体内部编写 RETURN 代码，因为 A）它更清楚发生了什么（你不仅仅是退出循环，你是从过程中返回），并且 B ）它更短。随心所欲。祝你好运。
回答by Tamás Kecskeméti
The simple loop. It's called simple for a reason: it starts simply with the LOOP keyword and ends with the END LOOP statement. The loop will terminate if you execute an EXIT, EXIT WHEN, or RETURN within the body of the loop (or if an exception is raised).
简单的循环。它被称为简单是有原因的：它以 LOOP 关键字开始，以 END LOOP 语句结束。如果您在循环体中执行 EXIT、EXIT WHEN 或 RETURN（或引发异常），则循环将终止。
回答by Ravindra HV
Following through with Tamás Kecskeméti's link, the only recommended way is to use a while loop with the desired condition specified in the beginning itself.
通过Tamás Kecskeméti的链接，唯一推荐的方法是使用 while 循环，并在开头指定所需的条件。
Below is and excerpt from the above link :
以下是上述链接的摘录：
Code Listing 5: A WHILE loop with one exit
PROCEDURE display_multiple_years (
start_year_in IN PLS_INTEGER
, end_year_in IN PLS_INTEGER)
IS
l_current_year PLS_INTEGER := start_year_in;
BEGIN
WHILE ( l_current_year <= end_year_in
AND total_sales_for_year (l_current_year) > 0)
LOOP
display_total_sales_for_year (l_current_year);
l_current_year := l_current_year + 1;
END LOOP;
END display_multiple_years;
回答by fabribara
define an exception, and when ever you want to exit raise and handle the exception as
定义一个异常，当你想退出 raise 并处理异常时
create procedure exit_loop_example as
exit_loop_exception exception;
begin
/* previous code block */
begin
for i in 1..20 loop
raise exit_loop_exception;
end loop;
exception when
exit_loop_exception then
/* handle exit loop*/
null;
end;
/* next code block */
end;
