Regex to find sub-string inside nested bracket followed by a specific string

Question

I am trying to find all the top level 'except' clauses from the below string.

where (
 param1 equals value1
 and
 param 2 equals valu2
 except (
  param3 equals value3
  where (
   param4 equals value4
   except (
     param6 equals value6
   )
  )
 )
)
except (
 param5 equal value5
)

Expected Result:

except (
  param3 equals value3
  where (
   param4 equals value4
   except (
     param6 equals value6
   )
  )
 )

&

 except (
     param5 equal value5
    )

I am new to regex and I was trying the below regex but its not working. except.((?:[^()]+|(?R))+)

Demo: https://regex101.com/r/AJZ1MV/1

You need to recurse Group 1 after adding parentheses around \(...\), except.*(\((?:[^()]++|(?1))*+\)) — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Sep 14, 2022 at 9:47
Thanks! This works fine in regex editor but not working with Orracle SQL REGEXP_SUBSTR. Any leads? — Chiranjit Bhattacharya
– Chiranjit Bhattacharya, Commented Sep 27, 2022 at 10:11
You must always provide the language where you are using the regex. Of course, Oracle POSIX based regex engine does not support lookarounds, nor does it support recursion and subroutines. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Sep 27, 2022 at 10:14
Yeah Thats my bad! Could you suggest any work around? Here is the sqlfidle sqlfiddle.com/#!4/13ba6c/4 — Chiranjit Bhattacharya
– Chiranjit Bhattacharya, Commented Sep 27, 2022 at 10:31
No, you cannot use a regex for this. You need a whole parser. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Sep 27, 2022 at 10:34

Briuor · Accepted Answer · 2022-09-18 02:11:53Z

0

This regex groups the cases you mentioned but must be improved:

(?:(?<=[\s])(except (?:.|\s)*)(?=except|\)))?|(?:(?<=\n)(except (?:.|\s)*)(?=$|\)))

Demo: https://regex101.com/r/20RAQV/1

answered Sep 18, 2022 at 2:11

Briuor

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1 Comment

Chiranjit Bhattacharya Over a year ago

Thanks for your response! This looks good in demo but not working with Oracle SQL. Actually I wanted to use it with SQL REGEXP_SUBSTR.

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