下面是一些PL/SQL代码的摘录,我认为展示一个PL/SQL错误:这是PL/SQL错误吗?
if guid_ is null then
dbms_output.put_line('guid_ is null: ' || guid_);
end if;
当这些线条被执行,它打印
guid_ is null: 07D242FCC55000FCE0530A30D4928A21
我在Oracle 11R2
select * from v$version;
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
PL/SQL Release 11.2.0.4.0 - Production
CORE 11.2.0.4.0 Production
TNS for IBM/AIX RISC System/6000: Version 11.2.0.4.0 - Production
NLSRTL Version 11.2.0.4.0 - Production
我可以用下面的类型和匿名块重现这一点。很抱歉的长度,但我相信我能不能缩短它了:
create type tq84_t as table of varchar2(32);
/
create type tq84_o as object (
dummy number(1),
not final member procedure clear
) not final;
/
show errors
create type tq84_d under tq84_o (
g varchar2(32),
constructor function tq84_d return self as result,
overriding member procedure clear
);
/
show errors
create package tq84_h as
t tq84_t;
end tq84_h;
/
show errors
create package body tq84_h as
begin
t := tq84_t();
end;
/
show errors
create type body tq84_o as
member procedure clear is begin
null;
end clear;
end;
/
create type body tq84_d as
constructor function tq84_d return self as result is
begin
g := sys_guid;
return;
end tq84_d;
overriding member procedure clear is begin
tq84_h.t.extend;
tq84_h.t(tq84_h.t.count) := g;
g := null;
end clear;
end;
/
show errors
declare
b tq84_o; -- Change to tq84_d ...
guid_ varchar2(32);
begin
b := new tq84_d;
guid_ := treat(b as tq84_d).g;
b.clear;
if guid_ is null then
dbms_output.put_line('guid_ is null: ' || guid_);
end if;
end;
/
drop type tq84_t;
drop type tq84_d;
drop type tq84_o;
drop package tq84_h;
还要注意,当我改变b tq84_o
到b tq84_d
,不会再出现错误。
有人可以验证这是否也发生在其他系统上?
我不确定这是为什么,但是当'if'条件被评估时,将'b tq84_o'改为'b tq84_d'会导致'guid_'不为空。添加一个打印类似语句的'else'语句证实了这一点。 – Allan 2014-11-14 15:20:28
我刚刚意识到错误是'如果guid_为null'则评估为true,而不是当'dbms_output'在变量应该为null时返回一个值。 – Allan 2014-11-14 15:24:21
此外,添加'else'会导致带有'b tq84_o'的版本按预期行事。 – Allan 2014-11-14 15:28:31