sql优化案例：oracle子查询的or 转为 union all以提升查询效率

select count(*) as y0_
  from CMS_CONTRACT this_
  left outer join CMS_SYS_USERS applier1_ on this_.APPLY_USER_ID = applier1_.id
 where
   (
       (
          this_.COST_TYPE in ('Income', 'Free', 'PayAndIncome', 'Financing') and
          applier1_.BUSINESS_GROUP_ID = 0
       )
       or
       this_.id in (select column_value from table(get_underling_contract_ids(249652)))
   )
   and this_.NUM_STATE in ('GENERATED');
  
  
  

实验区：
select sum(y0_) as y0_ from (
select count(*)  as y0_
  from CMS_CONTRACT this_
  left outer join CMS_SYS_USERS applier1_ on this_.APPLY_USER_ID = applier1_.id
 where
   (    
          this_.COST_TYPE in ('Income', 'Free', 'PayAndIncome', 'Financing') and
          applier1_.BUSINESS_GROUP_ID = 0  
   )
   and this_.NUM_STATE in ('GENERATED')
union all
select count(*)  as y0_
  from CMS_CONTRACT this_
  left outer join CMS_SYS_USERS applier1_ on this_.APPLY_USER_ID = applier1_.id
 where
   (    
          this_.id in (select column_value from table(get_underling_contract_ids(249652)))
   )
   and this_.NUM_STATE in ('GENERATED') and this_.COST_TYPE not in ('Income', 'Free', 'PayAndIncome', 'Financing') and
          applier1_.BUSINESS_GROUP_ID = 0 );