Re: Request to add feature to the Position function

On 03/27/2017 09:03 AM, Brian Dunavant wrote:
> That does not return the correct answer for the original poster's request.
>
> flpg=# select position('om' in reverse('Tomomasaaaaaaaaaaa'));
> position
> ----------
> 15
> (1 row)

It shows the position counting back from the end. If you want counting
from the front:

aklaver(at)test=> select (length('Tomomasaaaaaaaaaaa')+ 1) - position('om'
in reverse('Tomomasaaaaaaaaaaa'));
?column?
----------
4

>
>
>
>
> On Mon, Mar 27, 2017 at 11:43 AM, Adrian Klaver
> <adrian(dot)klaver(at)aklaver(dot)com> wrote:
>> On 03/27/2017 08:05 AM, Ron Ben wrote:
>>>
>>> Hi,
>>> position(substring in string)
>>> as listed here:
>>> https://www.postgresql.org/docs/9.1/static/functions-string.html
>>> locates sub string in a string.
>>>
>>> It doesn't support locateing the substring from the back.
>>>
>>> For example:
>>>
>>> position('om' in 'Tomomas')
>>> gives 2
>>>
>>> But if I want to locate the first occurance from the back of the string
>>> it's impossible/
>>
>>
>> aklaver(at)test=> select position('om' in reverse('Tomomas'));
>> position
>> ----------
>> 4
>>
>>
>>>
>>> My suggestion is to create a function
>>> position(substring in string,order)
>>> where order can be: begin, end
>>>
>>> and it will find the string according to this parameter.
>>> This is pretty easy to implement and should be a part of the PostgreSQL
>>> tools.
>>>
>>> similar fuctionality exists in trim function where user can specify
>>> leading or taling parameter
>>
>>
>>
>> --
>> Adrian Klaver
>> adrian(dot)klaver(at)aklaver(dot)com
>>
>>
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--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com