I like charindex() for this.

convert the int field to character and wrap in delimiters and then replace the commas in CSV with the delimiters and wrap in delimiters too.

SELECT '|' + LTRIM(STR(intField)) + '|', '|'+REPLACE(charFieldWithCSV,', ','|')+'|'

FROM TableWithIntField i

INNER JOIN TableWithCSVcharField ON CHARINDEX( '|' + LTRIM(STR(intField)) + '|', '|'+REPLACE(charFieldWithCSV,', ','|')+'|') >0;