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Thread: Escape wildcard problems.

Escape wildcard problems.

From
"Gauthier, Dave"
Date:

I read in the docs (section 9.7.1) that the backslash... \ ... is the default escape char to use in “like” expressions.  Yet when I try it, it doesn’t seem to work the ay I expect.  Here’s an example...

 

select name from templates where name like ‘%\_cont\_%’;

 

          name

----------------------------------

cgidvcontrol

x8idvcontrol

etc....

 

I would expect to NOT see these because the “cont” is not preceded by and followed by an underscore (because I escaped them with \).

 

Please advise.

 

Thanks

-dave

 

Re: Escape wildcard problems.

From
Sam Mason
Date:
On Fri, Oct 24, 2008 at 08:12:38AM -0700, Gauthier, Dave wrote:
> select name from templates where name like '%\_cont\_%';
>
>           name
> ----------------------------------
> cgidvcontrol
> x8idvcontrol
> etc....
>
> I would expect to NOT see these because the "cont" is not preceded by
> and followed by an underscore (because I escaped them with \).

You need to escape the escape! backslash is the escape character in
literals as well as like patterns, so you need to double it up.  I think
you want to be doing:

  name LIKE '%\\_cont\\_%'



  Sam

Re: Escape wildcard problems.

From
Alan Hodgson
Date:
On Friday 24 October 2008, "Gauthier, Dave" <dave.gauthier@intel.com> wrote:
> I read in the docs (section 9.7.1) that the backslash... \ ... is the
> default escape char to use in "like" expressions.  Yet when I try it, it
> doesn't seem to work the ay I expect.  Here's an example...
>
> select name from templates where name like '%\_cont\_%';
>

Use double \\ for underscores. I don't know why it's necessary, but it works
here.


--
Alan

Re: Escape wildcard problems.

From
Craig Ringer
Date:
Alan Hodgson wrote:
> On Friday 24 October 2008, "Gauthier, Dave" <dave.gauthier@intel.com> wrote:
>> I read in the docs (section 9.7.1) that the backslash... \ ... is the
>> default escape char to use in "like" expressions.  Yet when I try it, it
>> doesn't seem to work the ay I expect.  Here's an example...
>>
>> select name from templates where name like '%\_cont\_%';
>>
>
> Use double \\ for underscores. I don't know why it's necessary, but it works
> here.

Here's why. See the documentation for more information:


craig=> show standard_conforming_strings;
 standard_conforming_strings
-----------------------------
 off
(1 row)

craig=> SELECT '%\_cont\_%';
WARNING:  nonstandard use of escape in a string literal
LINE 1: SELECT '%\_cont\_%';
               ^
HINT:  Use the escape string syntax for escapes, e.g., E'\r\n'.
 ?column?
----------
 %_cont_%
(1 row)

craig=> SELECT E'%\\_cont\\_%';
  ?column?
------------
 %\_cont\_%
(1 row)

craig=> set standard_conforming_strings = 1;
SET

craig=> SELECT '%\_cont\_%';
  ?column?
------------
 %\_cont\_%
(1 row)



--
Craig Ringer

Re: Escape wildcard problems.

From
"Thom Brown"
Date:
Or you could use:

SELECT name
FROM templates
WHERE name ~ '\_cont\_';

This does it as a regular expression.

~* '\_aa\_';

On Fri, Oct 24, 2008 at 5:07 PM, Craig Ringer
<craig@postnewspapers.com.au> wrote:
> Alan Hodgson wrote:
>> On Friday 24 October 2008, "Gauthier, Dave" <dave.gauthier@intel.com> wrote:
>>> I read in the docs (section 9.7.1) that the backslash... \ ... is the
>>> default escape char to use in "like" expressions.  Yet when I try it, it
>>> doesn't seem to work the ay I expect.  Here's an example...
>>>
>>> select name from templates where name like '%\_cont\_%';
>>>
>>
>> Use double \\ for underscores. I don't know why it's necessary, but it works
>> here.
>
> Here's why. See the documentation for more information:
>
>
> craig=> show standard_conforming_strings;
>  standard_conforming_strings
> -----------------------------
>  off
> (1 row)
>
> craig=> SELECT '%\_cont\_%';
> WARNING:  nonstandard use of escape in a string literal
> LINE 1: SELECT '%\_cont\_%';
>               ^
> HINT:  Use the escape string syntax for escapes, e.g., E'\r\n'.
>  ?column?
> ----------
>  %_cont_%
> (1 row)
>
> craig=> SELECT E'%\\_cont\\_%';
>  ?column?
> ------------
>  %\_cont\_%
> (1 row)
>
> craig=> set standard_conforming_strings = 1;
> SET
>
> craig=> SELECT '%\_cont\_%';
>  ?column?
> ------------
>  %\_cont\_%
> (1 row)
>
>
>
> --
> Craig Ringer
>
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