CREATE TABLE `EMP_ATTEND` (
    `ATTEND_YMD` VARCHAR(8) NOT NULL COLLATE 'utf8_bin',
    `EMP_NO` VARCHAR(9) NOT NULL COLLATE 'utf8_bin'
)
COLLATE='utf8mb4_unicode_ci'
ENGINE=InnoDB;

DELIMITER $$
 
DROP FUNCTION IF EXISTS FNC_ATTEND;
 
CREATE FUNCTION FNC_ATTEND(attendType VARCHAR(10), empNo VARCHAR(10)) RETURNS BOOL
// CREATE FUNCTION  "FUNCTION 명" (변수값1 타입 , 변수값2 타입) RETURN 타입

BEGIN
	 //DECLARE 변수명 varchar(50); 변수선언	 
     DECLARE exist_flag INT;
     DECLARE returnVal  BOOL;
         SET returnVal = FALSE;
 
     -- 출석 등록
     IF 'attend'= attendType THEN
         SELECT COUNT(1)
           INTO exist_flag // 조회한 컬럼값인 CODE_NAME 을 변수에 넣는다.
           FROM EMP_ATTEND
          WHERE EMP_NO = empNo 
            AND ATTEND_YMD = DATE_FORMAT(NOW(), '%Y%m%d')
         ;
         
         IF exist_flag = 0 THEN
             INSERT INTO EMP_ATTEND(
                      ATTEND_YMD
                    , EMP_NO
             )VALUES(
                   DATE_FORMAT(NOW(), '%Y%m%d')
                     , empNo 
             );
             SET returnVal = TRUE;
         END IF;
     END IF;
      RETURN returnVal;
END $$
 
DELIMITER ;

-- if return value 0 then false
-- else if return value 1 then true
 
SELECT FNC_ATTEND('attend', '1000');