There are lots of articles and techniques onnthe internet about how to deal with delimited parameters. Last Wed I was visited a client that asked to write a quick query to return the data based on delimited values . Here we go
DECLARE @t VARCHAR(50)
SET @t = ('Bennet,smith')
WHERE ',' + @t + ',' LIKE '%,' + au_lname + ',%'
SELECT * FROM
authors WHERE CHARINDEX(',' + au_lname + ',',','+ @t+',')>0
As you can imagine, performance will be horrible.