Where value in column containing comma delimited values
WHERE
MyColumn LIKE '%,' + @search + ',%' --middle
OR
MyColumn LIKE @search + ',%' --start
OR
MyColumn LIKE '%,' + @search --end
OR
MyColumn = @search --single (good point by Cheran S in comment)
There is one tricky scenario. If I am looking for '40' in the list '17,34,400,12' then it would find ",40" and return that incorrect entry. This takes care of all solutions:
WHERE (',' + RTRIM(MyColumn) + ',') LIKE '%,' + @search + ',%'