Informix:选择空问题 [英] Informix: Select null problem
问题描述
使用Informix,我创建了一个临时表,试图从select语句中填充它.之后,我要进行更新,以在临时表中填充更多字段.
Using Informix, I've created a tempory table which I am trying to populate from a select statement. After this, I want to do an update, to populate more fields in the tempory table.
所以我正在做类似的事情;
So I'm doing something like;
create temp table _results (group_ser int, item_ser int, restype char(4));
insert into _results (group_ser, item_ser)
select
group_ser, item_ser, null
from
sometable
但是您不能选择null.
But you can't select null.
例如;
select first 1 current from systables
有效但是
select first 1 null from systables
失败!
(不要让我开始为什么不能不指定表就只做选择当前"之类的SQL Server!)
(Don't get me started on why I can't just do a SQL Server like "select current" with no table specified!)
推荐答案
此页面说不能这样做的原因是因为"NULL"没有类型.因此,解决方法是创建一个仅以所需类型返回NULL的sproc.
This page says the reason you can't do that is because "NULL" doesn't have a type. So, the workaround is to create a sproc that simply returns NULL in the type you want.
尽管这对我来说似乎是一个非常糟糕的解决方案.也许您可以在脚本中创建一个变量,将其设置为null,然后选择该变量?像这样:
That sounds like a pretty bad solution to me though. Maybe you could create a variable in your script, set it to null, then select that variable instead? Something like this:
DEFINE dummy INT;
LET dummy = NULL;
SELECT group_ser, item_ser, dummy
FROM sometable
这篇关于Informix:选择空问题的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!