什么时候应该嵌套PL/SQL BEGIN ... END块? [英] When should I nest PL/SQL BEGIN...END blocks?

问题描述

我似乎一直在随意地将BEGIN ... END块中的代码分段分组.通常，当我使用一个较长的存储过程并且需要一个临时变量时，我将只在那部分代码中声明它.当我要识别并处理为特定代码段引发的异常时，我也会这样做.

I've been somewhat haphazardly grouping subsections of code in BEGIN...END blocks when it seems right. Mostly when I'm working on a longer stored procedure and there's a need for a temporary variable in one spot I'll declare it just for that portion of the code. I also do this when I want to identify and handle exceptions thrown for a specific piece of code.

为什么要在一个过程，函数或另一个更大的PL/SQL块中嵌套块?还有其他原因吗?

Any other reasons why one should nest blocks within a procedure, function or another larger block of PL/SQL?

推荐答案

当您想像这样在本地处理异常时:

When you want to handle exceptions locally like this:

begin
   for emp_rec in (select * from emp) loop
      begin
         my_proc (emp_rec);
      exception
         when some_exception then
            log_error('Failed to process employee '||emp_rec.empno);
      end;
   end loop;
end;

在此示例中，处理了异常，然后我们继续处理下一个雇员.

In this example, the exception is handled and then we carry on and process the next employee.

另一种用法是声明范围有限的局部变量，如下所示:

Another use is to declare local variables that have limited scope like this:

declare
    l_var1 integer;
    -- lots of variables
begin
   -- lots of lines of code
   ...
   for emp_rec in (select * from emp) loop
      declare
         l_localvar integer := 0;
      begin
         -- Use l_localvar
         ...
      end
   end loop;

end;

请介意，这通常表明您的程序太大，应该分解:

Mind you, wanting to do this is often a sign that your program is too big and should be broken up:

declare
   l_var1 integer;
   -- lots of variables
   ...
   procedure local_proc (emp_rec emp%rowtype):
      l_localvar integer := 0;
   begin
      -- Use l_localvar
      ...
   end
begin
   -- lots of lines of code
   ...
   for emp_rec in (select * from emp) loop
      local_proc (emp_rec);
   end loop;

end; 

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