PL/SQL中双尖括号括起来的单词<<word>>
是什么意思?
我已经尝试过谷歌搜索,但谷歌会跳过标点符号。
它有什么用途?
<<倒计时>> for i in 1.9 loop blah; end loop 倒计时;
以下是示例: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;
/
输出结果为:
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
<>语法用于命名循环。当您有嵌套循环并需要使用EXIT loop_name WHEN ...语法来控制要退出的循环时非常有用。
请参见http://docs.oracle.com/cd/B28359_01/appdev.111/b28370/controlstructures.htm#BABJCCFJ以获取示例。
<<
和>>
是标签分隔符,因此在<<foo>>
中,foo
是一个标签。请查阅 Oracle 文档以了解更多信息:PL/SQL 语言基础 和 PL/SQL 控制语句。 - user272735