Search a key word in the whole column of that table - sql

Question

I have two tables.
User table
UserId Username
1 User1
2 User2
3 User3
4 User4
17 User17
18 User18
20 User20
And One more
Customer-Support table
CSid Userslist
1 1,3
2 2
3 20,17,18
How can I get the userids of the User Table are not present in Customer-Support Table..

Answer 1

Using a recursive common table expression to split the values should do it:
;WITH Split AS
(
SELECT
LEFT(Userslist,CHARINDEX(',',Userslist)-1) AS Userslist
,RIGHT(Userslist,LEN(Userslist)-CHARINDEX(',',Userslist)) AS Remainder
FROM CustomerSupport
WHERE Userslist IS NOT NULL AND CHARINDEX(',',Userslist)>0
UNION ALL
SELECT
Userslist AS Userslist, NULL AS Remainder
FROM CustomerSupport
WHERE Userslist IS NOT NULL AND CHARINDEX(',',Userslist)=0
UNION ALL
SELECT
LEFT(Remainder,CHARINDEX(',',Remainder)-1)
,RIGHT(Remainder,LEN(Remainder)-CHARINDEX(',',Remainder))
FROM Split
WHERE Remainder IS NOT NULL AND CHARINDEX(',',Remainder)>0
UNION ALL
SELECT
Remainder,null
FROM Split
WHERE Remainder IS NOT NULL AND CHARINDEX(',',Remainder)=0
)
SELECT * FROM Users
WHERE UserId NOT IN (
SELECT Userslist FROM Split)
The query will return User4 for your sample data as it's the only one missing in the CustomerSupport table.
Sample SQL Fiddle
I adapted my answer from this answer by KM. Credit to the one who deserves it.

Answer 2

The question is answerable with the current data-model, but it is a lot of work, complicated, and a sheer waste of time.
However, with a sensible data model, it is a very simple question, so I will answer it with such a model.
We remove the UsersList field from your Customer-Support table. It should never never never be there. No, really, never.
Now, assuming that, as your example data shows, every user can have one CSid, we will add a field CSid to your User Table. This is called a foreign key. Since, as you mention, not all users are linked to the CS Table, you make sure the field allows NULL values.
Now we fill in the data:
User table
UserId Username CSid
1 User1 1
2 User2 2
3 User3 1
4 User4 NULL
17 User17 3
18 User18 3
20 User20 3
And now, to answer your question:
SELECT * FROM UserTable WHERE CSid IS NULL;
Your question is a very good example why it pays to think about your data model before messing it up. Your query is extremely simple, if your data model makes sense.