Re: question about regexp_substr

Not sure what do you mean, I did this:

select regexp_substr('A1B2C3D4E', '[^0-9]*', 1, 1) occur_1,
       regexp_substr('A1B2C3D4E', '[^0-9]*', 1, 2) occur_2,
       regexp_substr('A1B2C3D4E', '[^0-9]*', 1, 3) occur_3,
       regexp_substr('A1B2C3D4E', '[^0-9]*', 1, 4) occur_4,
       regexp_substr('A1B2C3D4E', '[^0-9]*', 1, 5) occur_5

O O O O O
- - - - -
A B C

select regexp_substr('A1B2C3D4E', '[^0-9]+', 1, 1) occur_1,
       regexp_substr('A1B2C3D4E', '[^0-9]+', 1, 2) occur_2,
       regexp_substr('A1B2C3D4E', '[^0-9]+', 1, 3) occur_3,
       regexp_substr('A1B2C3D4E', '[^0-9]+', 1, 4) occur_4,
       regexp_substr('A1B2C3D4E', '[^0-9]+', 1, 5) occur_5

O O O O O
- - - - -
A B C D E

And I dont understand very well why * gives A, B and C whereas + gives expected output.

This is how I read it,

regexp_substr('A1B2C3D4E', '[^0-9]*', 1, 1) says start searching from position 1 for first pattern which is non-numeric and no matter if there is any pattern occurence so A is printed
regexp_substr('A1B2C3D4E', '[^0-9]*', 1, 1) says start searching from position 1 for second pattern which is non-numeric and no matter if there is any pattern occurence. If I parse the line A is non-numeric therefore is a candidate but I am looking for the second occurence so I keep on searching, immediately see number 1 so the pattern is not matched so keep on searching, we now read B which is non-numeric, satisfies the pattern so it should be printed but it's not?

2014-12-16 22:42 GMT+01:00 Jackie Brock <J.Brock_at_cablelabs.com>:
>
> J Run it with various values where the three is – get the first
> occurrence, then the second, then the third, then the fourth – you’ll
> easily see what it’s doing.
>
>
>
> *From:* amonte [mailto:ax.mount_at_gmail.com]
> *Sent:* Tuesday, December 16, 2014 2:30 PM
> *To:* Jackie Brock
> *Cc:* Oracle-L Group
> *Subject:* Re: question about regexp_substr
>
>
>
> Hello Jackie
>
> I know + means > 1 and * > 0 occurence. But I dont see why they give
> different results in my example.
>
> I understand that what query is asking with * is
>
> "find in the string any non-numeric character pattern, no matter if the
> there is character or not in the third occurence". I dont see why B
> satisfies such condition?
>
>
>
> Thanks in advance
>
>
>
> Alex
>
>
>
> 2014-12-16 22:23 GMT+01:00 Jackie Brock <J.Brock_at_cablelabs.com>:
>
> The plus sign indicates that it expects at least 1 digit (1 or more). The
> * means 0 or more.
>
>
>
> *From:* oracle-l-bounce_at_freelists.org [mailto:
> oracle-l-bounce_at_freelists.org] *On Behalf Of *amonte
> *Sent:* Tuesday, December 16, 2014 2:07 PM
> *To:* Oracle-L Group
> *Subject:* question about regexp_substr
>
>
>
> Hi people
>
> I have some difficulty understanding applying an operator to the pattren
> in regexp_substr. Not sure if anyone can help ?
>
> The question is, what is the difference between these two queries:
>
> select regexp_substr('A1B2C3D4E', '[^0-9]+', 1, 3) from dual;
>
> R
> -
> C
>
> select regexp_substr('A1B2C3D4E', '[^0-9]*', 1, 3) from dual;
>
> R
> -
> B
>
> Why * and + gives different answers?
>
> Thanks in advance
>
>
>
> Alex
>

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