Distinct在MySQL的过程中不起作用 如果（eventType=1），则 设置@Whereclause=CONCAT（@Whereclause，“and scheduleDate>”，@currentdate，“order by scheduleDate”）； 如果结束； 如果（eventType=0），则 设置@Whereclause=CONCAT（@Whereclause，“和scheduleDate

，则我们必须在选择列表中按列排序，如下所示：

任一：

    if(eventType=1  ) then
     set @Whereclause=CONCAT(@Whereclause," and  scheduleDate > ",@currentdate, " order by  scheduleDate " );
    end if;
     if(eventType=0  ) then
     set @Whereclause=CONCAT(@Whereclause," and  scheduleDate < ",@currentdate," order by  scheduleDate  desc " );
    end if;
     if(eventType=-1 ) then 
      set @Whereclause=CONCAT(@Whereclause," order by  scheduleDate  desc  " );
      end if;

   set @SqlQuery=  CONCAT("
select   distinct(event_schedule_id)
 from TEST_EVENT_LIST_VIEW ", @Whereclause );


set totalcountquery=@Whereclause;

  if(offsetvalue<recordlimit) then  

      set @QueryfforPagination=CONCAT(@SqlQuery," limit ",recordlimit );
     PREPARE querystatement FROM @QueryfforPagination;
     EXECUTE querystatement;
     DEALLOCATE PREPARE querystatement;


    else 
       set  @QueryfforPagination=CONCAT(@SQLQuery," limit ",recordlimit," offset ",offsetvalue);
       PREPARE querystatement FROM @QueryfforPagination;
       EXECUTE querystatement;
       DEALLOCATE PREPARE querystatement;

    end if;


END

或

 order by  event_schedule_id desc

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如果我们从上面删除DISTINCT，那么所有语句都可以正常工作。

如何修复？首先，您必须弄清楚您想要什么。。。

set @SqlQuery=  CONCAT("
select   distinct event_schedule_id, scheduleDate
from TEST_EVENT_LIST_VIEW ", @Whereclause );

SELECT DISTINCT A FROM myTable ORDER BY B --It doesn't work
SELECT DISTINCT A FROM myTable ORDER BY A --It works
SELECT DISTINCT A, B FROM myTable ORDER BY A, B --It works
SELECT DISTINCT A, B FROM myTable ORDER BY B --It works