SQL Query to replace characters by getting record list from other table - sql

Question

I wrote the below query to take an id as input, get DocumentID from Attachment table and then use that id to get Document name from Document table. Once i get document name i am removing anything but the character a-z and numbers. The below Query is working fine if only one Document id is being returned based on Entity id, how can i make it work if one entity id returns more than one Document ID. I also need to return all those new names as well.
ALTER PROCEDURE [dbo].[NormalizeDocumentFileName1]
-- Add the parameters for the stored procedure here
#id nvarchar(16),
#temp varchar(50) OUTPUT
AS
BEGIN
  Select #temp=Document.TheName from Document where id = (Select DocumentId from Attachment where EntityId = #id)
  Declare #KeepValues as varchar(50)
  Set #KeepValues = '%[^a-z0-9-_.]%'
  While PatIndex(#KeepValues, #temp) > 0
  Set #temp = Stuff(#temp, PatIndex(#KeepValues, #temp), 1, '')
   
END

Answer 1

Personally, I would go with a very different approach with this. I'm going to make use of Alan Burstein's NGrams8K.
You want to avoid the WHILE loop, it'll perform awfully, and go with a dataset approach. I'm going to use a Function instead:
CREATE FUNCTION NormalizeDocumentFileName (#FileName varchar(50) )
RETURNS TABLE
AS RETURN
WITH Tokens AS (
SELECT *
FROM dbo.NGrams8k (#FileName,1) --If you didn't create the function on the dbo schema, you'll need to change it.
WHERE token NOT LIKE '%[^a-z0-9-_.]%')
SELECT CONVERT(varchar(50),(SELECT Token + ''
FROM Tokens
ORDER BY Position
FOR XML PATH(''))) AS NormalFileName;
GO
Then you can do something as simple as:
SELECT D.YourColumn, NDFN.NormalFileName
FROM Document D
CROSS APPLY NormalizeDocumentFileName(D.TheName) NDFN;

Answer 2

Another set-based function for this type of thing is PatExclude8K the function does the same thing as what Larnu put together and is reusable. You would have to use the link to get the T-SQL code to create the function. The function works like this:
DECLARE #string varchar(50) = '$$$123___!!!555.ABC???';
SELECT * FROM dbo.patexclude8k(#string, '[^A-Za-z0-9-_.]');
Returns:
NewString
------------
123___555.ABC
Note that what LARNU put together will return entity references for XML characters such as "&", ">", etc. But it will perform better than Patexclude. If you don't expect to deal special XML characters you can use a slightly modified version that will perform relatively the same - here it is:
CREATE FUNCTION dbo.PatExclude8K_NXP
(
#String VARCHAR(8000),
#Pattern VARCHAR(50)
)
/*******************************************************************************
Purpose:
Given a string (#String) and a pattern (#Pattern) of characters to remove,
remove the patterned characters from the string.
Usage:
--===== Basic Syntax Example
SELECT CleanedString
FROM dbo.PatExclude8K_NXP(#String,#Pattern);
--===== Remove all but Alpha characters
SELECT CleanedString
FROM dbo.SomeTable st
CROSS APPLY dbo.PatExclude8K(st.SomeString,'%[^A-Za-z]%');
--===== Remove all but Numeric digits
SELECT CleanedString
FROM dbo.SomeTable st
CROSS APPLY dbo.PatExclude8K(st.SomeString,'%[^0-9]%');
Programmer Notes:
1. #Pattern is case sensitive (the function can be easily modified to make it so)
2. There is no need to include the "%" before and/or after your pattern since since we
are evaluating each character individually
Revision History:
Rev 00 - 20180508 Initial Development - Alan Burstein
*******************************************************************************/
RETURNS TABLE WITH SCHEMABINDING AS
RETURN
WITH
E1(N) AS (SELECT N FROM (VALUES (NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL)) AS X(N)),
itally(N) AS
(
SELECT TOP(CONVERT(INT,LEN(#String),0)) ROW_NUMBER() OVER (ORDER BY (SELECT NULL))
FROM E1 T1 CROSS JOIN E1 T2 CROSS JOIN E1 T3 CROSS JOIN E1 T4
)
SELECT NewString =
(
SELECT SUBSTRING(#String,N,1)
FROM iTally
WHERE 0 = PATINDEX(#Pattern,SUBSTRING(#String COLLATE Latin1_General_BIN,N,1))
FOR XML PATH('')
);
Lastly, both NGrams8K and PatExclude perform quite a bit better when the optimizer chooses a parallel execution plan. To force a parallel plan you can use Make_parallel by Adam Machanic. Using Larnu's solution as an example you would force a parallel plan like so:
SELECT D.YourColumn, NDFN.NormalFileName
FROM Document D
CROSS APPLY NormalizeDocumentFileName(D.TheName) NDFN;
CROSS APPLY dbo.make_parallel();

Answer 3

Hmmm. You can dispense with the while loop and use a recursive CTE:
with cte as (
Select d.TheName, 0 as lev, d.TheName as orig_TheName
from Document d
where d.id = (Select DocumentId from Attachment where EntityId = #id)
union all
select Stuff(cte.thename, PatIndex(#KeepValues, cte.thename), 1, '') as DocumentId lev + 1, cte.orig_TheName
from cte
where PatIndex(#KeepValues, cte.thename) > 0
)
select theName
from (select theName, max(lev) over (partition by orig_thename) as max_lev
from cte
) x
where lev = max_lev