oracle 求两表数据去重复语句优化,该怎么解决

oracle 求两表数据去重复语句优化
sql如下，此条sql已经效率很低，求教效率搞的sql语句。谢谢各位！

SQL code

SELECT *  FROM LCD29 L WHERE L.LDCD291 >= TRUNC(SYSDATE, 'dd')   AND L.GDAB056 NOT IN       (SELECT B.BD_DATA5          FROM HR_COMBOOKDATE B         WHERE B.BD_DATE >= TRUNC(SYSDATE, 'dd')           AND TRUNC(L.LDCD291, 'dd') = TRUNC(B.BD_DATE, 'dd'));

SQL code

SELECT L.*  FROM LCD29 L  inner join HR_COMBOOKDATE B on TRUNC(L.LDCD291, 'dd') = TRUNC(B.BD_DATE, 'dd') AND L.GDAB056 = B.BD_DATA5 WHERE L.LDCD291 >= TRUNC(SYSDATE, 'dd')   and B.BD_DATE >= TRUNC(SYSDATE, 'dd');
[解决办法]
SELECT 1更多的时候是用在NOT EXISTS，即不存在，不存在 符合  
FROM HR_COMBOOKDATE B
  WHERE B.BD_DATE >= TRUNC(SYSDATE, 'dd')
……
这些关联条件的记录。为了迎合sql语法，需要select一个字段，那么就select 1吧，当然，select 2 也可以。