Extract value before one symbol and stop after another one in SQL

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Extract value before one symbol and stop after another one in SQL

JeremyU

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Points: 640
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August 22, 2023 at 11:30 pm

#4268548

Hello,
I am trying to extract Event Name from a long string that has some information not relevant for what I am doing at the very moment. I basically need to extract everything after 2nd '_' and before 3rd '_'.
So technically I need to get Bestseller and Promotion for the examples that I am showing in the picture.
I believe we usually can extract such things with SUBSTRING, but here the number of characters before and after is unknown.
SELECT rl_event_id
Extract value after 2nd '_' and stop before 3rd '_'
Please let me know if someone has ideas.

As for charindex function, I am not 100% sure how I can use it in this situation.
It gives me 0 or 16.
When I do it second time it just gives me 0s.

There must be another way to do it. I am not sure how I can approach it in a different way.

Viewing 5 posts - 1 through 4 (of 4 total)

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Phil Parkin SSC Guru Points: 246985 More actions · Answer 1

Here is a possibility.

You could so it all in a single (rather lengthy) expression, but I broke it out to help you understand how I did it.

Please provide consumable test data in future.

WITH SomeText
AS (SELECT t = 'AB123456_BlahBlah_BESTSELLER_blahBlah')
SELECT SomeText.t
      ,c1.t1
      ,c2.t2
      ,Ext = LEFT(c2.t2, CHARINDEX ('_', c2.t2) - 1)
FROM SomeText
    CROSS APPLY
(SELECT t1 = STUFF (SomeText.t, 1, CHARINDEX ('_', SomeText.t), '')) c1
    CROSS APPLY
(SELECT t2 = STUFF (c1.t1, 1, CHARINDEX ('_', c1.t1), '')) c2;

The absence of evidence is not evidence of absence.
Martin Rees

You can lead a horse to water, but a pencil must be lead.
Stan Laurel

Michael L John One Orange Chip Points: 27060 More actions · Answer 2

Idea#1

Are these values known? It looks like there is a "fixed list" of possible values. If so, then you can skip parsing the string and do a like. The issue here is that the leading wildcards may be a performance issue.

CASE
  WHEN String LIKE '%Bestseller%' THEN 'Bestseller'
  WHEN String LIKE '%Promotion%' THEN 'Promotion'

Idea #2

Leverage Jeff Moden's string splitter HERE.

SELECT * 
FROM [dbo].[DelimitedSplit8K] (
   'ABC_123_XYZ_789'
  ,'_')
WHERE ItemNumber = 3

Michael L John
If you assassinate a DBA, would you pull a trigger?
To properly post on a forum:
http://www.sqlservercentral.com/articles/61537/

Phil Parkin SSC Guru Points: 246985 More actions · Answer 3

I vote for using the splitter. For some reason, I'd forgotten that even existed when I posted earlier.

The absence of evidence is not evidence of absence.
Martin Rees

You can lead a horse to water, but a pencil must be lead.
Stan Laurel

ScottPletcher SSC Guru Points: 101121 More actions · Answer 4

I think CHARINDEXes might be somewhat more efficient here:

;WITH data AS (
    SELECT rl_event_id = 'AB123456_BlahBlah_BESTSELLER_blahBlah'
)
SELECT rl_event_id, SUBSTRING(rl_event_id, pos_of_second_underscore + 1, pos_of_third_underscore - pos_of_second_underscore - 1)
FROM data
CROSS APPLY ( SELECT CHARINDEX('_', rl_event_id) ) AS ca1(pos_of_first_underscore)
CROSS APPLY ( SELECT CHARINDEX('_', rl_event_id, pos_of_first_underscore + 1) ) AS ca2(pos_of_second_underscore)
CROSS APPLY ( SELECT CHARINDEX('_', rl_event_id, pos_of_second_underscore + 1) ) AS ca3(pos_of_third_underscore)

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