Question

即使fruit_batch_info中没有记录，我也确实希望在我的AP01 结果，所以我使用左联接。

但是，一旦我添加“ where fruit_batch_info = 11”，我的AP01就不再出现在我的结果中。

如何将AP01保存在结果中？

要求： 报告“ all_fruits”中的所有记录以及有关“ fruit_batch = 11”的所有信息

所需结果

ID  , DESC   , BATCH, STORAGE 
----- -------- ------ ------------
APO1, Apple  , null , null  
PE01, Pear   , 11   , Warehouse-11
KU01, Kumquat, 11   , Warehouse-11

这是我的查询：

with all_fruits as
(select 'AP01' as fruit_id, 'Apple' as fruit_desc from dual union all
 select 'PE01' as fruit_id, 'Pear' as fruit_desc from dual union all
 select 'KU01' as fruit_id, 'Kumquat' as fruit_desc from dual),
 fruit_batch_info as
 (select 'PE01' as fruit_id, '10' as fruit_batch , 'Warehouse-10' as fruit_storage from dual union all
  select 'PE01' as fruit_id, '11' as fruit_batch , 'Warehouse-11' as fruit_storage from dual union all
  select 'PE01' as fruit_id, '12' as fruit_batch , 'Warehouse-12' as fruit_storage from dual union all
  select 'KU01' as fruit_id, '10' as fruit_batch , 'Warehouse-10' as fruit_storage from dual union all
  select 'KU01' as fruit_id, '11' as fruit_batch , 'Warehouse-10' as fruit_storage from dual)

 select a.fruit_id  , 
        fruit_desc, 
        fruit_batch,
        fruit_storage
 from all_fruits  a 
 left join fruit_batch_info i  on a.fruit_id = i.fruit_id
 where i.fruit_batch='11'

Answer 1

使用LEFT JOIN时，将该表中的条件添加到联接ON子句中，而不是WHERE子句中：

left join fruit_batch_info i  on a.fruit_id = i.fruit_id and i.fruit_batch='11'

如何在此左联接中保留空记录？

1 个答案: