Re: What does LIKE '%%' actually do in a WHERE clause?

From: Norman Dunbar <oracle@xxxxxxxxxxxxxxx>
To: oracle-l@xxxxxxxxxxxxx
Date: Fri, 07 Oct 2011 08:52:19 +0100

Morning Grant,

> Maybe I'm mis-interpreting things, but wouldn't LIKE '%' actually be 
> semantically equivalent to IS NOT NULL.  That is, for something to be LIKE 
> "anything", it must therefore be known (or more specifically knowable) in 
> order to evaluate its "likeness".
Yes, to all intents and purposes, they are equivalent. I haven't checked 
if the CBO considers them to be the same though!

> The %% thing is however, new and interesting to me :)
It had me foxed as well. I'd never seen it until this came up, and I 
thought it was a special format of the wildcard - I admit that at first 
I thought it was a way of specifying the percent sign - why would they 
be looking for a string like '%' came to mind! ;-)



Cheers,
Norm.

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Norman Dunbar
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Follow-Ups:

Re: What does LIKE '%%' actually do in a WHERE clause?
From: Subodh Deshpande

References:
- What does LIKE '%%' actually do in a WHERE clause?
  - From: Dunbar, Norman (Capgemini)
- Re: What does LIKE '%%' actually do in a WHERE clause?
  - From: Stephane Faroult
- Re: What does LIKE '%%' actually do in a WHERE clause?
  - From: Grant Allen

Re: What does LIKE '%%' actually do in a WHERE clause?

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