这是一个会导致错误的情况：

create table mutate (
    x NUMBER,y NUMBER
);

insert into mutate (x,y)
values (1,2);

insert into mutate (x,y)
values (3,4);

我创建了两行.现在我通过调用这个语句来加倍我的行：

insert into mutate (x,y)
select x + 1,y + 1 
from mutate;

复制错误并不是绝对必要的,但稍后会对我的演示有所帮助.所以表格的内容如下所示：

X,Y
1,2
3,4
2,3
4,5

一切都很好.现在有趣的部分：

create or replace function mutate_count
return PLS_INTEGER
is
    v_dummy PLS_INTEGER;
begin
    select count(*) 
    into v_dummy
    from mutate;

    return v_dummy;
end mutate_count;
/

我创建了一个函数来查询我的表并返回一个计数.现在,我将结合INSERT语句：

insert into mutate (x,y)
select x + 2,y + 2
from mutate
where mutate_count() = 4;

结果？这个错误：

ORA-04091: table MUTATE is mutating,trigger/function may not see it
ORA-06512: at "MUTATE_COUNT",line 6

所以我知道是什么原因造成的错误,但我很好奇为什么. Oracle不执行SELECT,检索结果集,然后执行这些结果的批量插入？如果在查询完成之前已经插入了记录,我只会期待一个突变表的错误.但是如果Oracle做到了,那么以前的语句不会

insert into mutate (x,y + 1 
from mutate;

启动无限循环？

更新：

通过Jeffrey的链接,我发现在the Oracle docs年：

By default,Oracle guarantees statement-level read consistency. The
set of data returned by a single query is consistent with respect to a
single point in time.

his post年的作者也有评论：

One could argue why Oracle doesn’t ensure this ‘statement-level read
consistency’ for repeated function calls that appear inside a sql
statement. It could be considered a bug as far as I’m concerned. But
this is the way it currently works.

我假设在Oracle 10和11版本之间这种行为发生了变化吗？