使用完全联接但不使用左联接时出现问题。为什么？

Question

当我在不同的数据库上使用left join时，它可以工作，但是当我使用inner join时却不能。为什么呢

SELECT tkblue_tklabel_dev_data.EmailContent.*, tkblue_tklabel_dev_archdata.EmailTracking.*
FROM tkblue_tklabel_dev_data.EmailContent
FULL JOIN tkblue_tklabel_dev_archdata.EmailTracking ON tkblue_tklabel_dev_archdata.EmailTracking.idEmailTracking = tkblue_tklabel_dev_data.EmailContent.idEmailTracking

  

未知表'tkblue_tklabel_dev_data.EmailContent'

但是使用时

SELECT tkblue_tklabel_dev_data.EmailContent.*, tkblue_tklabel_dev_archdata.EmailTracking.*
FROM tkblue_tklabel_dev_data.EmailContent
LEFT JOIN tkblue_tklabel_dev_archdata.EmailTracking ON tkblue_tklabel_dev_archdata.EmailTracking.idEmailTracking =
tkblue_tklabel_dev_data.EmailContent.idEmailTracking

我没有此错误消息，但只能得到左表的结果。或者，我希望所有结果都像完全加入一样。

Answer 1

完全连接在mysql中不存在，但是您可以在UNION中同时使用左连接和右连接来产生相同的结果

SELECT tkblue_tklabel_dev_data.EmailContent.*
      , tkblue_tklabel_dev_archdata.EmailTracking.*
FROM tkblue_tklabel_dev_data.EmailContent
LEFT JOIN tkblue_tklabel_dev_archdata.EmailTracking  
  ON tkblue_tklabel_dev_archdata.EmailTracking.idEmailTracking = tkblue_tklabel_dev_data.EmailContent.idEmailTracking
UNION 
SELECT tkblue_tklabel_dev_data.EmailContent.*
      , tkblue_tklabel_dev_archdata.EmailTracking.*
FROM tkblue_tklabel_dev_data.EmailContent
RIGHT JOIN tkblue_tklabel_dev_archdata.EmailTracking  
  ON tkblue_tklabel_dev_archdata.EmailTracking.idEmailTracking = tkblue_tklabel_dev_data.EmailContent.idEmailTracking