update

mec-biz/src/main/resources/config/mybatis/PracticeGroupMapper.xml

@@ -413,7 +413,8 @@
     </resultMap>
     <select id="queryStudentBuys" resultMap="queryStudentBuysMap">
         SELECT o.`name_` organ_name_,a.student_id_,u.`username_` student_name_,u.phone_,a.lastClassDate last_class_date_,
-        b.firstBuyTime first_buy_time_,DATEDIFF(b.firstBuyTime,a.lastClassDate) interval_day_,
+        b.firstBuyTime first_buy_time_,
+        CASE WHEN DATEDIFF(b.firstBuyTime,a.lastClassDate) &lt; 0 THEN 0 ELSE DATEDIFF(b.firstBuyTime,a.lastClassDate) END interval_day_,
         CASE WHEN b.firstBuyTime IS NULL THEN 0 ELSE 1 END buy_practice_ FROM
         (SELECT pg.`student_id_` ,max(concat(cs.`class_date_`,' ',cs.`end_class_time_` )) lastClassDate
         FROM `practice_group` pg