How to return data containing the same value within a string?

I have been asked to gather data where all strings within the defaultmessage column are similar, the issue is the message is unknown and so is the string count value, I have no information to search for in the WHERE clause. I have tried to run a SELF JOIN however, this did not work as it just returned all values, the table contains over 10000 rows of data, where the strings vary but are sometimes similar to each other, could someone please explain how I could go about to return this?

Table: This is just an example table of what I am trying to gather

So basically, I need to gather data where the default message is the same across different ids, please let me know if you require further information, tried to explain this the best I could.

Please note again, I have no idea what the default message actually specifies, I just need to find entries of data that have the same message within the column

Output:

>Solution :

On SQL Server, we could use COUNT() as a window function here:

WITH cte AS (
    SELECT *, COUNT(*) OVER (PARTITION BY DefaultMessage) cnt
    FROM yourTable
)

SELECT TravellerID, Traveller, DefaultMessage
FROM cte
WHERE cnt > 1
ORDER BY DefaultMessage, TravellerID;