Question

以下内容摘自我在检查backup_schedule表中的schema_info值后创建逻辑备份的过程：

CREATE OR REPLACE PROCEDURE BACKUP_EXECUTE 
(
  [...]
) AS 
[...]
  schemas varchar2(255):=' ';

  cursor schema_name is select upper(schema_name) schema_name from schema_info
    where backup_schedule like '%'||to_char(sysdate, 'D')||'%'
    and exists (select * from dba_users where username=upper(schema_name));

  type sl is table of schema_name%ROWTYPE
    index by pls_integer;

  schema_list sl;
BEGIN
  open schema_name;

  fetch schema_name bulk collect into schema_list;

  close schema_name;
  if schema_list.count != 0 then

    for indx in 1..schema_list.count loop      
      if(schemas not like '%'||schema_list(indx).schema_name||'%') then
        if indx>1 then
          schemas:=schemas||',';
        else
          schemas:=null;
        end if;
        schemas:=schemas||''''||schema_list(indx).schema_name||'''';
      end if;
    end loop;

  [...]
  end if;

  EXCEPTION
  [...]
END;

除了事实，这可以做得更好，我想专注于一件事。我们知道like不符合null值。我应该保留上面的代码并写下一些后来被删除的起始值，还是最好在nvl(schemas,' ')语句中使用if？

使用类似于varchar2的启动时具有空值

0 个答案: