oracle 12c - select string after last occurrence of a character

问题

I have below string:

ThisSentence.ShouldBe.SplitAfterLastPeriod.Sentence

So I want to select Sentence since it is the string after the last period. How can I do this?

回答1:

You can probably do this with complicated regular expressions. I like the following method:

select substr(str, - instr(reverse(str), '.') + 1)

Nothing like testing to see that this doesn't work when the string is at the end. Something about - 0 = 0. Here is an improvement:

select (case when str like '%.' then ''
             else substr(str, - instr(reverse(str), ';') + 1)
        end)

EDIT:

Your example works, both when I run it on my local Oracle and in SQL Fiddle.

I am running this code:

select (case when str like '%.' then ''
             else substr(str, - instr(reverse(str), '.') + 1)
        end)
from (select 'ThisSentence.ShouldBe.SplitAfterLastPeriod.Sentence' as str from dual) t

回答2:

Just for completeness' sake, here's a solution using regular expressions (not very complicated IMHO :-) ):

select regexp_substr(
  'ThisSentence.ShouldBe.SplitAfterLastPeriod.Sentence',
  '[^.]+$') 
from dual

The regex

uses a negated character class to match anything except for a dot [^.]
adds a quantifier + to match one or more of these
uses an anchor $ to restrict matches to the end of the string

回答3:

And yet another way.

Not sure from a performance standpoint which would be best...

The difference here is that we use -1 to count backwards to find the last . when doing the instr.

  With CTE as 
  (Select 'ThisSentence.ShouldBe.SplitAfterLastPeriod.Sentence' str, length('ThisSentence.ShouldBe.SplitAfterLastPeriod.Sentence') len from dual)
  Select substr(str,instr(str,'.',-1)+1,len-instr(str,'.',-1)+1) from cte;

回答4:

how many dots in a string?

select length(str) - length(replace(str, '.', '') number_of_dots from ...

get substring after last dot:

select substr(str, instr(str, '.', 1, number_of_dots)+1) from ...

来源：https://stackoverflow.com/questions/24084644/oracle-12c-select-string-after-last-occurrence-of-a-character

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