oracle 在where中使用or之后查询字段不走索引

这个是原本的sql，直接执行的时候在执行计划中可以看到3张表是直接全表扫描了。

我分别将2个条件进行了拆分，每次只执行一个结果如下：

我又将sql写法改成了union all ，也是走索引的，所以我想问问大家，是不是使用了or一定就不会走索引了？

 记账表的索引列我也放在下面的截图了：

具体的sql如下，证件号我去掉了：

select b.olrptno c1,
       b.caseno c2,
       b.oolrptno c3,
       case
         when a.clmstate = '70' then
          '0'
         else
          '1'
       end c4,
       c.systemname c5,
       (select h.codename
          from ldcode h
         where h.codetype = 'clmstate'
           and trim(a.clmstate) = trim(h.code)) c6,
       (select auditidea from llclaimuwmain where clmno = a.rgtno) c7,
       a.rgtdate c8,
       a.endcasedate c9,
       b.customername c10,
       nvl(c.StandbyFlag3, 0) c11,
       (select nvl(sum(lb.realpay), 0)
          from llclaimdetail lb
         where lb.caseno = b.caseno
           and lb.givetype = '0') c12,
       a.grpcontno c13,
       (select count(1) from llcasereceipt la where la.caseno = b.caseno) c14,
       b.remark c15,
       a.togetherflag c16,
       b.condoleflag c17,
       case
         when c.makedate is null then
          a.rgtdate
         else
          c.makedate
       end c18,
       decode(a.riskcode, '211701', 'Y', 'N') c19
  from llregister a
 inner join llcase b
    on a.rgtno = b.rgtno
  left join llclaimprt c
    on c.rptno = b.oolrptno
 inner join lcinsured d
    on d.contno = b.contno
 where 1 = 1
   and ((d.name = '张松' and d.idtype = '0' and d.idno = '') or
       b.customerno in
       (select lg.customerno
           from lcinsuredrelated lg
          inner join lcinsured jj
             on jj.contno = lg.contno
          inner join ldperson lh
             on lg.maincustomerno = lh.customerno
          where floor(MONTHS_BETWEEN(sysdate, jj.birthday) / 12) < 18
            and lh.name = '张松'
            and lh.idtype = '0'
            and lh.idno = ''))

第一个or查询语句左边有三个键的联合索引，但是右边没有。在SQL当中，or语句如果有一个字段没有索引的话是不会走索引的。所以尽量避免使用or