Question

我尝试使用uid获取first_name和last_name，并从FILE_ATTACH_INFO表中获取url使用相同的uid。我在下面尝试但看起来它不起作用，因为它们有不同数量的列。我怎样才能做到这一点？

    SELECT first_name, last_name 
        FROM `USER` AS a 
        WHERE uid = '00283366-85df-4c1b-9d94-7beafb8d44fd'
UNION 
    SELECT url
        FROM `FILE_ATTACH_INFO`
        WHERE user_id = '00283366-85df-4c1b-9d94-7beafb8d44fd'

我希望得到

first_name   |   last_name   |   url
------------------------------------------------
kim          |     asdf      |  https://qwef.com

Answer 1

Select * FROM `USER`  a JOIN `FILE_ATTACH_INFO` b on a.uid = b.user_id WHERE a.uid = '00283366-85df-4c1b-9d94-7beafb8d44fd'

尝试内部联接...

Answer 2

SELECT a.first_name, a.last_name, b.url 
        FROM USER AS a 
        LEFT OUTER JOIN FILE_ATTACH_INFO b ON a.uid = b.user_id
        WHERE a.uid = '00283366-85df-4c1b-9d94-7beafb8d44fd'

Answer 3

因为您使用了错误的操作，所以只有在两个表的列相同时才能应用union。在这种情况下，您需要在它们共享的列上连接两个表。

SELECT u.first_name, u.last_name, fa.url FROM 
user  u
INNER JOIN file_attach_info  fa
  on u.uid = fa.user_id

Answer 4

尝试这个

SELECT a.first_name,a.last_name,f.url FROM USER AS a INNER JOIN FILE_ATTACH_INFO AS f ON f.user_id=a.uid WHERE 1;

如何组合来自两个不同表的数据？

4 个答案: