MySQL 相鄰兩條數據相減

<!-- 計算每兩次消費的間隔天數 -->
SELECT B.MEN_ID,TIMESTAMPDIFF(DAY,B.PRE_DATE,B.CURR_DATE) AS DAYS FROM 
(
    <!-- 行變列 -->
    SELECT A.MEN_ID,A.ORDER_DATE AS CURR_DATE,@A.ORDER_DATE AS PRE_DATE,@A.ORDER_DATE:= A.ORDER_DATE
    FROM TBL_MAS_ORDER_MASTER A,(SELECT @A.ORDER_DATE:=NULL) S
) B WHERE B.PRE_DATE IS NOT NULL