Remove items in csv string

Provide us sample data so we know what do deal with.

ok, here is a sample of what we are working with.

Table 1

customers      |      products
1                    |      aaa,bbb,ccc
2                    |      ddd,eee,fff
3                    |      bbb,ccc,ggg
4                    |      ppp,sss,ttt
5                     |      fff,qqq,mmm
6                    |      ooo,nnn,ddd


Table 2 (NOT VALID ITEMS LIST Or NOT EXISTS Results (insert into a temp table))

Customers      |      Products
1                    |      bbb
3                    |      ccc
4                    |      ppp


--Query to do the following

Results should be deleting the CSV value from table 2 products from the products in table1 since they are no longer valid
customers      |      products
1                    |      aaa,ccc
2                    |      ddd,eee,fff
3                    |      bbb,ggg
4                    |      sss,ttt
5                    |      fff,qqq,mmm
6                    |      ooo,nnn,ddd

So you can see that we removed 'bbb' for customer 1 and 'ccc' for customer 3  and 'ppp' for customer 4 from the actual csv string.

My suggestion is to use the following solution:

UPDATE t1
SET t1.products = REPLACE(t1.products,t2.products,'')
FROM table1 t1
	INNER JOIN table2 t2 ON t1.customers = t2.customers

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This will remove those products in table1 but will let double commas (when removed from the middle of the string), initial commas (where removing from the beginning of the string and final commas (when removing from the end of the string) so you'll need to run the following update to sort out this situation:

UPDATE table1
SET products = CASE
		WHEN LEFT(products,1)=',' THEN RIGHT(products,LEN(products)-1)
		WHEN RIGHT(products,1)=',' THEN LEFT(products,LEN(products)-1)
		ELSE REPLACE(products,',,',',')
	END

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Careful, that could destroy your data!

Thanks guys, i'm still testing this. the only thing i forgot was that the original string had spaces after the commas so the case when is missing some when statements

customers      |      products
1                    |      aaa, bbb, ccc
2                    |      ddd, eee, fff
3                    |      bbb, ccc, ggg
4                    |      ppp, sss, ttt
5                     |      fff, qqq, mmm
6                    |      ooo, nnn, ddd

You just need to add the space in the REPLACE function in the ELSE statement and consider 2 characters for the other situations:

UPDATE table1
SET products = CASE
	WHEN LEFT(products,2)=', ' THEN RIGHT(products,LEN(products)-2)
	WHEN RIGHT(products,2)=' ,' THEN LEFT(products,LEN(products)-2)
	ELSE REPLACE(products,', ,',',')
	END

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NOTE: Do not run this in your Production environment before testing it in a Development environment.

so i'm still analyzing this and for some reason in my live table it will remove the first results from my update query but won't update the other items that meet my criteria from the temp table.

UPDATE dbo.livetable
SET product = REPLACE(t1.product,t2.product,'')
FROM dbo.livetable as t1
	INNER JOIN #update t2 ON t1.customers = t2.customers AND t1.location = t2.location AND t1.programId = t2.programid

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