一、問題描述  三表聯合查詢  按主表的時間倒敘並分頁

　　下面sql語句 ORDER BY失效 ，如果把 ORDER BY  放在最後 比如有20條資料 第一頁會是10 -1 第二頁是20-11  分頁不正確

　　查詢資料發現：在mysql5.7中，如果不加limit，系統會把order by優化掉。

 　　在mysql5.7手冊的8.2.2.1中有解釋：

　　子查詢的優化是使用半連線的策略完成的(The optimizer uses semi-join strategies to improve subquery execution)

　　使用半連線進行優化，子查詢語句必須滿足一些標準(In MySQL, a subquery must satisfy these criteria to be handledas a semi-join)。

　　其中一個標準是:必須不是一個包含了limit和order by的語句(It must not have ORDER BY with LIMIT.)

　　解決方法一：子查詢裡外都排序   

　　解決方法二：在嵌入一個子查詢（好像也是裡外都排序）

　　SELECT * FROM (
　　SELECT * FROM (
　　SELECT * FROM zs_safe_confess B WHERE B.ENABLE = 1 ORDER BY B.CREATE_TIME DESC, B.UPDATE_TIME DESC LIMIT 0,10) A
　　LEFT JOIN zs_safe_confess_content C ON A.ID = C.CSAFE_ID)D
　　LEFT JOIN zs_resources ON D.ID = zs_resources.ID AND zs_resources.TYPE = 10 AND zs_resources.ENABLE = 1
　　ORDER BY D.CREATE_TIME DESC, D.UPDATE_TIME DESC

SELECT A.*,
        zs_safe_confess_content.CID,
        zs_safe_confess_content.CSAFE_ID,
        zs_safe_confess_content.CSTATUS,
        zs_safe_confess_content.CCONTENT,
        zs_safe_confess_content.CCHECK_RESULT,
        zs_safe_confess_content.CCREATE_TIME,
        zs_safe_confess_content.CUPDATE_TIME,
        zs_safe_confess_content.CUSER_ID,
        zs_safe_confess_content.CUSER_NAME,
        zs_safe_confess_content.CENABLE,
        zs_safe_confess_content.CBACKUP_01,
        zs_safe_confess_content.CBACKUP_02,
        zs_safe_confess_content.CBACKUP_03,
        zs_resources.RID AS RID,
        zs_resources.ID AS ID,
        zs_resources.TYPE AS RTYPE,
        zs_resources.URL AS RURL,
        zs_resources.RESOURCE_CODE AS RRESOURCE_CODE,
        zs_resources.FILE_NAME AS RFILE_NAME,
        zs_resources.FILE_SIZE AS RFILE_SIZE,
        zs_resources.CREATOR AS RCREATOR,
        zs_resources.CREATETIME AS RCREATETIME,
        zs_resources.MODIFIER AS RMODIFIER,
        zs_resources.UPDATETIME AS RUPDATETIME,
        zs_resources.ENABLE AS RENABLE FROM (
        SELECT
        zs_safe_confess.ID,
        zs_safe_confess.SAFE_NAME, zs_safe_confess.DEPT_NAME,
        zs_safe_confess.DEPT_ID, zs_safe_confess.PROJECT_NAME,
        zs_safe_confess.PROJECT_NUMBER,
        zs_safe_confess.PROJECT_PERSON,
        zs_safe_confess.WORK_ADDRESS, zs_safe_confess.WORK_NUMBER,
        zs_safe_confess.COMPANY_PERSON, zs_safe_confess.COMPANY_PHONE,
        zs_safe_confess.FACTORY_PERSON,
        zs_safe_confess.FACTORY_PHONE,
        zs_safe_confess.DANGER_DISCERN, zs_safe_confess.ENVIRONMENT_DISCREN,
        zs_safe_confess.DANGER_MEASURES,zs_safe_confess.ENVIRONMENT_MEASURES,
        zs_safe_confess.DANGER_MANAGER, zs_safe_confess.MANAGER_TIME,
        zs_safe_confess.SCENE_COMFIRM, zs_safe_confess.SCENE_COMFIRM_TIME,
        zs_safe_confess.COMFIRM_CHECK_PERSON,
        zs_safe_confess.COMFIRM_CHECK_TIME,
        zs_safe_confess.TEST_BEFORE_PERSON, zs_safe_confess.TEST_BEFORE_TIME,
        zs_safe_confess.TEST_PERSON,
        zs_safe_confess.TEST_TIME,
        zs_safe_confess.TEST_AFTER_PERSON,zs_safe_confess.TEST_AFTER_TIME,zs_safe_confess.STATUS,zs_safe_confess.TYPE
        ,zs_safe_confess.CREATE_TIME,zs_safe_confess.UPDATE_TIME,zs_safe_confess.USER_ID,zs_safe_confess.USER_NAME,zs_safe_confess.ENABLE
        ,zs_safe_confess.BACKUP_01,zs_safe_confess.BACKUP_02,zs_safe_confess.BACKUP_03
        FROM zs_safe_confess WHERE zs_safe_confess.ENABLE = 1 ORDER BY CREATE_TIME DESC, UPDATE_TIME DESC
 
 LIMIT 0,10) A 
        LEFT JOIN zs_safe_confess_content ON A.ID = zs_safe_confess_content.CSAFE_ID  
        LEFT JOIN zs_resources ON A.ID = zs_resources.ID  AND zs_resources.TYPE = 10 AND zs_resources.ENABLE = 1 (ORDER BY A.CREATE_TIME DESC, A.UPDATE_TIME DESC)(這是解決方法一)