Question

我正在尝试编写一个PL / SQL函数来存储带有变量表名的select语句（我知道这有点奇怪，但实际上这是一个很好的设计决定）。以下代码不起作用......但我不确定如何同时获取变量表名称（构建查询）并返回数据集。有人有这方面的经验吗？ TIA。

CREATE OR REPLACE FUNCTION fn_netstat_all (casename in varchar2) 
RETURN  resultset_subtype
IS
  dataset resultset_subtype;
  v_sql varchar2(25000);
  v_tablename varchar2(50);

begin

  v_sql := 'SELECT * FROM ' || casename || '_netstat;'; 

  OPEN dataset FOR
    execute immediate v_sql;
  return dataset;

end;

Answer 1

如果你的resultset_subtype是ref_cursor（或者只是用ref_cursor替换resultset_subtype），你可以：

CREATE OR REPLACE
FUNCTION fn_netstat_all (
   casename IN VARCHAR2
)
RETURN resultset_subtype
IS
   dataset resultset_subtype;
BEGIN
   OPEN dataset
   FOR 'SELECT * FROM ' || casename || '_netstat';

   RETURN dataset;
END fn_netstat_all;

FWIW，您可能希望查看DBMS_ASSERT包以包装casename变量，以帮助防止动态SQL中的SQL注入攻击。

希望它有所帮助...

Answer 2

下面假设所有表都相似。也可以在不使用DBMS_SQL的情况下选择每个表中相似的列的子集。我也注意到Ollie提到的SQL注入。

create table so9at (
  id number(1),
  data varchar2(5)
);

insert into so9at values (1, 'A-AAA');
insert into so9at values (2, 'A-BBB');
insert into so9at values (3, 'A-CCC');

create table so9bt (
  id number(1),
  data varchar2(5)
);

insert into so9bt values (5, 'B-AAA');
insert into so9bt values (6, 'B-BBB');
insert into so9bt values (7, 'B-CCC');

create table secret_identities (
  cover_name varchar2(20),
  real_name varchar2(20)
);

insert into secret_identities values ('Batman', 'Bruce Wayne');
insert into secret_identities values ('Superman', 'Clark Kent');

/* This is a semi-secure version immune to certain kind of SQL injections. Note
that it can be still used to find information about any table that ends with
't'. */
create or replace function cursor_of (p_table_id in varchar2)
return sys_refcursor as
  v_cur sys_refcursor;
  v_stmt constant varchar2(32767) := 'select * from ' || dbms_assert.qualified_sql_name(p_table_id || 't');
begin
  open v_cur for v_stmt;
  return v_cur;
end;
/
show errors

/* This is an unsecure version vulnerable to SQL injection. */
create or replace function vulnerable_cursor_of (p_table_id in varchar2)
return sys_refcursor as
  v_cur sys_refcursor;
  v_stmt constant varchar2(32767) := 'select * from ' || p_table_id || 't';
begin
  open v_cur for v_stmt;
  return v_cur;
end;
/
show errors

create or replace procedure print_values_of (p_cur in sys_refcursor) as
  type rec_t is record (
    id number,
    data varchar2(32767)
  );
  v_rec rec_t;
begin
  fetch p_cur into v_rec;

  while p_cur%found loop
    dbms_output.put_line('id = ' || v_rec.id || ' data = ' || v_rec.data);
    fetch p_cur into v_rec;
  end loop;

end;
/
show errors

declare
  v_cur sys_refcursor;
begin
  v_cur := cursor_of('so9a');
  print_values_of(v_cur);
  close v_cur;

  v_cur := cursor_of('so9b');
  print_values_of(v_cur);
  close v_cur;

  /* SQL injection vulnerability */
  v_cur := vulnerable_cursor_of('secret_identities --');
  dbms_output.put_line('Now we have a cursor that reveals all secret identities. Just see DBMS_SQL.DESCRIBE_COLUMNS ...');
  close v_cur;

  /* SQL injection made (mostly) harmless - will throw ORA-44004: invalid qualified SQL name */
  v_cur := cursor_of('secret_identities --');
  close v_cur;
end;
/

使用PL / SQL和变量表名返回数据集

2 个答案: