Question

PL / SQL中双角括号中单词的含义是什么，例如。 <<word>>？

我试图进行谷歌搜索，但谷歌会跳过标点符号。

它用于什么？

Answer 1

如问题评论者所述，这用于标记复合语句以及GOTO的目标。您可以使用END和END LOOP中的标签来提高可读性，例如<<countdown>> for i in 1.9 loop blah; end loop countdown;

以下是一个例子：

set echo on
set serveroutput on

<<begin_end_block>> 
declare 
  msg varchar2(1000);
begin
  dbms_output.enable;
  msg := chr(9) || 'start';
  <<loopblk>> 
  for itr8 in 1 .. 5
  loop
    msg := msg || chr(10) || chr (9) ||  'loop';
    dbms_output.put_line ('Iterator is ' || itr8);
    <<ifblck>> if itr8 > 2
    then
      msg := msg || chr(10) || chr(9) || 'greater than 2';
      goto gototarg;
    end if;
    exit loopblk when mod (itr8, 4) = 0;
    continue loopblk;
    <<gototarg>>
    dbms_output.put_line ('after goto target');
  end loop loopblk;
  dbms_output.put_line ('Ending, here are the messages' || chr(10) || msg);
end begin_end_block;
/

输出是：

anonymous block completed
Iterator is 1
Iterator is 2
Iterator is 3
after goto target
Iterator is 4
after goto target
Iterator is 5
after goto target
Ending, here are the messages
    start
    loop
    loop
    loop
    greater than 2
    loop
    greater than 2
    loop
    greater than 2

Answer 2

＆lt;＆gt;语法用于命名循环。当你有嵌套循环并需要使用EXIT loop_name WHEN ...语法来控制退出哪个循环时很有用。

请参阅http://docs.oracle.com/cd/B28359_01/appdev.111/b28370/controlstructures.htm#BABJCCFJ以获取示例

PL / SQL＆lt; <word>＆gt; </word>的含义是什么？

2 个答案: