Update or delete splitted data - sql

Question

In customers table I have Email column which could contain multiple emails separated by (;).
I used split function to separate emails for each customer:
Cust1 --->email1
cust1 --->email2
cust1 ---> emailN
And I could add more emails to the same customer.
I want to be able to update or delete the splitted emails, in other words if email2= abc#company.com I want to change it to xyz#company.com or delete it.
Is it possible to do using split function? or any other way?
Here is my split function
CREATE FUNCTION [dbo].[fnSplitString]
(
#string NVARCHAR(MAX),
#delimiter CHAR(1)
)
RETURNS #output TABLE(splitdata NVARCHAR(MAX)
)
BEGIN
DECLARE #start INT, #end INT
SELECT #start = 1, #end = CHARINDEX(#delimiter, #string)
WHILE #start < LEN(#string) + 1 BEGIN
IF #end = 0
SET #end = LEN(#string) + 1
INSERT INTO #output (splitdata)
VALUES(SUBSTRING(#string, #start, #end - #start))
SET #start = #end + 1
SET #end = CHARINDEX(#delimiter, #string, #start)
END
RETURN
END
Calling the function to split emails:
select tb1.custId, split.splitdata from customers tb1
outer apply [dbo].[fnSplitString] (tb1.email,';') split
where tb1.Email like '%;%'
To add new email to the same customer:
UPDATE Customers set Email=Email+';new Email' Where CustId='customerId'
for updating or deleting existing emails, any suggestions?
Thanks in advance

Answer 1

First things first, your split function is not optimal. It's doing the split in an RBAR fashion. There are number of ways to do this in a set-based fashion. Here is one using XML, taken from Aaron Bertrand's article.
I prefer Jeff Moden's DelimitedSplit8K, but for simplicity's sake, I'll use the XML split.
CREATE FUNCTION dbo.SplitStrings_XML
(
#List NVARCHAR(MAX),
#Delimiter NVARCHAR(255)
)
RETURNS TABLE
WITH SCHEMABINDING
AS
RETURN
(
SELECT Item = y.i.value('(./text())[1]', 'nvarchar(4000)')
FROM
(
SELECT x = CONVERT(XML, '<i>'
+ REPLACE(#List, #Delimiter, '</i><i>')
+ '</i>').query('.')
) AS a CROSS APPLY x.nodes('i') AS y(i)
);
Now that you have your set-based splitter, it's time for the CRUD operations:
To SELECT the splitted emails:
SELECT
c.CustomerId,
Email = s.Item
FROM Customer c
CROSS APPLY dbo.SplitStrings_XML(c.Emails, ';') s
To ADD new Email to a particular Customer:
DECLARE #email NVARCHAR(100) = 'abc#company.com'
UPDATE Customer
SET Emails = Emails + ';' + #email
WHERE
CustomerId = 1
AND CHARINDEX(#email, Emails) = 0 -- Prevent duplicate Email
To UPDATE an existing Email of a Customer:
DECLARE #to_update NVARCHAR(100) = 'abc#company.com',
#new_email NVARCHAR(100) = 'xyz#company.com';
;WITH Cte AS(
SELECT
c.CustomerId,
Email = CASE WHEN s.Item = #to_update THEN #new_email ELSE s.Item END
FROM Customer c
CROSS APPLY dbo.SplitStrings_XML(c.Emails, ';') s
)
UPDATE c
SET Emails = STUFF((
SELECT ';' + Email
FROM Cte
WHERE CustomerId = c.CustomerId
FOR XML PATH(''), type).value('.[1]','nvarchar(max)')
,1, 1, '')
FROM Customer c
SELECT * FROM Customer
You could also use REPLACE:
UPDATE Customer
SET Emails = REPLACE(Emails, #to_update, #new_email)
WHERE CustomerId = 1
To DELETE an existing Email from the list:
DECLARE #to_delete NVARCHAR(100) = 'abc#company.com';
;WITH Cte AS(
SELECT
c.CustomerId,
Email = s.Item
FROM Customer c
CROSS APPLY dbo.SplitStrings_XML(c.Emails, ';') s
WHERE s.Item <> #to_delete
)
UPDATE c
SET Emails = STUFF((
SELECT ';' + Email
FROM Cte
WHERE CustomerId = c.CustomerId
FOR XML PATH(''), type).value('.[1]','nvarchar(max)')
,1, 1, '')
FROM Customer c
SELECT * FROM Customer
You could also use REPLACE:
DECLARE #to_delete NVARCHAR(100) = 'abc#company.com';
UPDATE Customer
SET Emails = REPLACE(Emails, #to_delete + ';', '')
WHERE CustomerId = 1
Now, I'll leave it as exercise for you to convert these into stored procedures. :)