insert
INSERT INTO T_USER (USER_SEQ_N , USER_ID_V , USER_NM_V , USER_PWD_V , REG_D , USE_YN_C )VALUES( (SELECT NVL(MAX(USER_SEQ_N)+1, 1) FROM T_USER) , 'user_id_0' || (SELECT NVL(MAX(USER_SEQ_N)+1, 1) FROM T_USER) , 'user_nm_0' || (SELECT NVL(MAX(USER_SEQ_N)+1, 1) FROM T_USER) , 'a12345' , SYSDATE , 'Y' )