如何应用`REGEXP_SUBSTR`从字符串中提取特定的substring？

Question

I have the following string 011/2020-PL00-70-31 (it could slightly different for example 011/2020-PL00-70-3 or 011/2020-PL00-70-310 ). I need to extract from the string all string before last - . As a result of REGEXP_SUBSTR of 011/2020-PL00-70-310 I need to get 011/2020-PL00-70 only, ie without last 4 symbols (but in some case it could be without 2 or 3 symbols).

I am new to regular expression in PL SQL, so sorry for question if it is so easy.

Thanks a lot.

Answer 1

In this particular case I think you're overthinking your solution using regex. You're hyphen is always the third hyphen so you can just use INSTR to find the third occurrence. See this query here:

SELECT SUBSTR(sample, 1, INSTR(sample, '-', 1, 3)-1) AS match
FROM sample_table;

I have linked my results with a SQLFiddle - http://sqlfiddle.com/#!4/c30207/7/0

Answer 2

You can use a regex capture group () to get only the part you need from a pattern.

SELECT REGEXP_SUBSTR(sample, '^(.*)-\d+$',1,1,'',1) AS sample2
FROM sample_table

SAMPLE2
011/2020-PL00-70
011/2020-PL00-70
011/202-PL00-70

Demo on db<>fiddle here

Test of the regex pattern here

Answer 3

You might just replace the trailing digits away:

REGEXP_REPLACE(whatever, '(-[^-]+)$', '')

The regex catches a minus sign and any subsequent non-minus characters ( [^-]+ ; alternatively you can match against digits only: \d+ ) – if they are located at the end of the string ( $ ), so intermediate digits are protected.