Define variable to use with IN operator (T-SQL)

Question

I have a Transact-SQL query that uses the IN operator. Something like this:

select * from myTable where myColumn in (1,2,3,4)

Is there a wa

Answer 1

This one uses PATINDEX to match ids from a table to a non-digit delimited integer list.

-- Given a string @myList containing character delimited integers 
-- (supports any non digit delimiter)
DECLARE @myList VARCHAR(MAX) = '1,2,3,4,42'

SELECT * FROM [MyTable]
    WHERE 
        -- When the Id is at the leftmost position 
        -- (nothing to its left and anything to its right after a non digit char) 
        PATINDEX(CAST([Id] AS VARCHAR)+'[^0-9]%', @myList)>0 
        OR
        -- When the Id is at the rightmost position
        -- (anything to its left before a non digit char and nothing to its right) 
        PATINDEX('%[^0-9]'+CAST([Id] AS VARCHAR), @myList)>0
        OR
        -- When the Id is between two delimiters 
        -- (anything to its left and right after two non digit chars)
        PATINDEX('%[^0-9]'+CAST([Id] AS VARCHAR)+'[^0-9]%', @myList)>0
        OR
        -- When the Id is equal to the list
        -- (if there is only one Id in the list)
        CAST([Id] AS VARCHAR)=@myList

Notes:

• when casting as varchar and not specifying byte size in parentheses the default length is 30
• % (wildcard) will match any string of zero or more characters
• ^ (wildcard) not to match
• [^0-9] will match any non digit character
• PATINDEX is an SQL standard function that returns the position of a pattern in a string