oracle多条件外连接执行计划
（1）
select host.id from itr_host_v host left join itr_ci_ref r on host.id = r .to_ci
                                                   and r.from_template_id =
                                                       '0301010101' ;



（2）                                                     
select host.id   from itr_host_v   host, itr_ci_ref r  where   host.id = r. to_ci(+)
                                                   and  r.from_template_id(+) =
                                                       '0301010101';
                                                   
（3）
select host.id   from itr_host_v   host, itr_ci_ref r  where   host.id = r. to_ci(+)
                                                   and  r.from_template_id =
                                                       '0301010101';

（4）select host.id from itr_host_v host left join itr_ci_ref r on host.id = r .to_ci
                                                  where r.from_template_id =
                                                       '0301010101' ;

上面三条sql，1==2，不等于3。3==4;1是多条件的左外连接。4是单条件左外连接。

（1）、（2)的执行计划为