How can I use SQL Substring to extract characters from this filename? - sql

Question

I'm attempting to use the SUBSTRING function to extract a name out of a filename.
An example filename would be: "73186_RHIMagnesita_PHI_StopLoss_TruncSSN_NonRedact_Inc_to_Apr2022_Paid_to_Apr2022_EDIT"
I'm attempting to extract the "RHIMagnesita" from this filename.
The substring I used was:
SUBSTRING(DFH.FileName, CHARINDEX('_', DFH.FileName) + 1, CHARINDEX('_PHI', DFH.FileName) - 1)
The results it gave were: "RHIMagnesita_PHI_S"
How do I extract only "RHIMagnesita" using the Substring function?

Answer 1

The third parameter in SUBSTRING is length not position, so you would need to substract the length of the beginning string.
SUBSTRING(DFH.FileName, CHARINDEX('_', DFH.FileName) + 1, CHARINDEX('_PHI', DFH.FileName) - CHARINDEX('_', DFH.FileName))
You might need to add or substract 1, but that's the idea.

Answer 2

You were close. You need to use CHARINDEX to also find the position of the second underscore.
SELECT SUBSTRING(FileName,
CHARINDEX('_', FileName) + 1,
CHARINDEX('_', FileName, CHARINDEX('_', FileName) + 1) -
CHARINDEX('_', FileName) - 1) AS FilePart
FROM yourTable;

Answer 3

Here's a way using STRING_SPLIT and FETCH, rather than SUBSTRING We split the string and only return the second row
SELECT
value
FROM STRING_SPLIT('73186_RHIMagnesita_PHI_StopLoss_TruncSSN_NonRedact_Inc_to_Apr2022_Paid_to_Apr2022_EDIT','_')
ORDER BY (SELECT NULL)
OFFSET 1 ROWS
FETCH NEXT 1 ROWS ONLY;
Note: On Azure Sql Server STRING_SPLIT has an ordinal parameter, so you could write this
SELECT
value
FROM
STRING_SPLIT('73186_RHIMagnesita_PHI_StopLoss_TruncSSN_NonRedact_Inc_to_Apr2022_Paid_to_Apr2022_EDIT','_', 1)
WHERE ordinal = 2