日付が悪い日は分秒でSQLを表します.

文章の起源:http://blog.csdn.net/wzy0623/article/details/7684513
 
皬日付と時間の差の日数:
トムDays(end time)-To_Days(startime)
  
皱二日付/時間の差の秒数:
SELECT UNIX_TIMESTAMP-UNIX_TIMESTAMP(start time);　
  
皰日付と時間の差の時の点数:
SELECT SEC_TOTIME(UNIXUTIMESTAMP(end time)-UNIXUTIMESTAMP(start time);
 
 
MySQL実現方式:

SET @a:=UNIX_TIMESTAMP(NOW()) - UNIX_TIMESTAMP(CURRENT_DATE());

--      set   a    SQL   

SELECT CONCAT(IF(TRUNCATE(@a/24/3600,0)=0,'',CONCAT(TRUNCATE(@a/24/3600,0),' ')),
              IF(MOD(TRUNCATE(@a/3600,0),24)=0,'',CONCAT(MOD(TRUNCATE(@a/3600,0),24),'  ')),
              IF(MOD(TRUNCATE(@a/60,0),60)=0,'',CONCAT(MOD(TRUNCATE(@a/60,0),60),' ')),
              IF(MOD(@a,60)=0,'',CONCAT(MOD(@a,60),' '))) dt_diff;

 
oracle実現方式:

WITH a
             AS (SELECT   SYSDATE - TRUNC(SYSDATE) tt
                   FROM DUAL)
        SELECT    DECODE (TRUNC (tt, 0), 0, NULL, TRUNC (tt, 0) || ' ')
               || DECODE (TRUNC (MOD (tt, 1) * 24, 0),
                          0, NULL,
                          TRUNC (MOD (tt, 1) * 24, 0) || '  ')
               || DECODE (TRUNC (MOD (tt * 24, 1) * 60, 0),
                          0, NULL,
                          TRUNC (MOD (tt * 24, 1) * 60, 0) || ' ')
               || DECODE (ROUND (MOD (tt * 24 * 60, 1) * 60, 0),
                          0, NULL,
                          ROUND (MOD (tt * 24 * 60, 1) * 60, 0) || ' ')
                  dt_diff
          FROM a;