--使用IN的时候 SELECT keyCol, CASE WHEN keyCol IN ( SELECT keyCol FROM tbl_B ) THEN 'Matched' ELSE 'Unmatched' END Label FROM tbl_A;
--使用EXISTS的时候 SELECT keyCol, CASE WHEN EXISTS ( SELECT * FROM tbl_B WHERE tbl_A.keyCol = tbl_B.keyCol ) THEN 'Matched' ELSE 'Unmatched' END Label FROM tbl_A;
