给DB数据表加强制索引

• DB2 数据库会根据DB层的统计值决定 根据查询条件走哪一个索引，某些情况下，由于未知原因，索引会走偏，故程序中可以规定程序走哪一个索引来避免索引走偏的情况发生。

强制走索引的 实例代码如下：

 SELECT vbeln
       zorgdn
       vstel
       zstaff
       zvtweg
       vsbed zacty
       zlifsk  erdat lfdat AS zdtday zebeln
    INTO CORRESPONDING FIELDS OF TABLE it_likp
    FROM likp
    WHERE    vbeln IN s_vbeln
    AND erdat IN s_erdat
    AND lfart = 'ZCRE'
    AND vstel IN r_vstel
    AND zebeln IN s_zebeln
    AND zorgdn = space
   AND lfdat IN s_zpldat
 %_HINTS DB6 '<IXSCAN TABLE=''LIKP'' SAP_INDEX=''Z06'' />'. "#EC CI_HINTS
 
 %_hints db6 '&SUBSTITUTE LITERALS&'.                      "#EC CI_HINTS
 
 where    vbeln in s_vbeln
                and erdat in s_erdat
                and lfart = 'ZCRE'
                and vstel in r_vstel
                and zebeln in s_zebeln
                and zorgdn = space
               and lfdat in s_zpldat
 * %_HINTS DB6 '&max_blocking_factor 5&' "#EC CI_HINTS
 %_hints db6 '&SUBSTITUTE LITERALS&'.