Обсуждение: Like Command returning wrong result set

Hello group,

 

I’m writing a script and a bit confused on the results with the like command.

 

gm.title like 'CP_%'

 

The above command gives me records with titles like CP_40, CP_2, CP_23, etc.

 

gm.title like '%_CT'

 

The above command give me records with tiles like Quiz: RadiInterpretation w/ CBCT.

 

I was expecting it to return titles that contained *_CT, i.e. FX_CT or DR_CT.  It’s as if it’s ignoring the underscore the way it would do if you were using ‘%CT’.  Does it ignore the underscore when it’s right after the ‘%’?

> On Aug 5, 2021, at 07:00, Tchouante, Merlin <mtchouan@umaryland.edu> wrote:
>
> Hello group,
>
> I’m writing a script and a bit confused on the results with the like command.
>
> gm.title like 'CP_%'
>
> The above command gives me records with titles like CP_40, CP_2, CP_23, etc.
>
> gm.title like '%_CT'

Somewhat confusingly, '_' is the single-character wildcard for SQL's LIKE operation:

xof=# SELECT 'A' LIKE '_';
 ?column?
----------
 t
(1 row)

You can escape it to search for it literally:

xof=# SELECT '_' LIKE '\_';
 ?column?
----------
 t
(1 row)

xof=# SELECT 'A' LIKE '\_';
 ?column?
----------
 f
(1 row)

This worked, thank you so much; I'm still stuck in Oracle mode.  Thank you to everyone that responded.

Thanks,
  -- Merlin
 
 
Merlin D. Tchouante, Sr. IT Enterprise Application Developer
Center for Information Technology Services (CITS) 
601 West Lombard Street 
Baltimore, Maryland 21201-1512 
mtchouan@umaryland.edu  
410-706-4489 * 410-706-1500 fax

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-----Original Message-----
From: Christophe Pettus <xof@thebuild.com> 
Sent: Thursday, August 5, 2021 10:05 AM
To: Tchouante, Merlin <mtchouan@umaryland.edu>
Cc: pgsql-sql@postgresql.org
Subject: Re: Like Command returning wrong result set

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> On Aug 5, 2021, at 07:00, Tchouante, Merlin <mtchouan@umaryland.edu> wrote:
>
> Hello group,
>
> I’m writing a script and a bit confused on the results with the like command.
>
> gm.title like 'CP_%'
>
> The above command gives me records with titles like CP_40, CP_2, CP_23, etc.
>
> gm.title like '%_CT'

Somewhat confusingly, '_' is the single-character wildcard for SQL's LIKE operation:

xof=# SELECT 'A' LIKE '_';
 ?column?
----------
 t
(1 row)

You can escape it to search for it literally:

xof=# SELECT '_' LIKE '\_';
 ?column?
----------
 t
(1 row)

xof=# SELECT 'A' LIKE '\_';
 ?column?
----------
 f
(1 row)