Question

我正在尝试加入两个表格。表1称为帐户，它由account_id，fname，lname，picture组成，表2称为friendpending，由account_id，friend_id和message组成。我正在创建一个允许用户添加朋友的程序，当我传入account_id时，它返回用户名，我需要它来返回friend_id名称。

这是我到目前为止所尝试的：

SELECT account.fname, account.lname, account.picture
from account
INNER JOIN friendpending ON account.account_id = friendpending.account_id
WHERE friendpending.account_id = p_account_id;

Answer 1

如果您想要朋友的表格中的朋友姓名，那么您需要选择该字段（或字段）：

SELECT friendpending.name, 
    account.fname, account.lname, account.picture 
FROM account INNER JOIN friendpending ON account.account_id = friendpending.account_id
WHERE friendpending.account_id = p_account_id;

或

SELECT friendpending.fname, friendpending.lname, account.picture  
FROM account INNER JOIN friendpending ON account.account_id = friendpending.account_id
WHERE friendpending.account_id = p_account_id;

或者，根据以下评论ON account.account_id = friendpending.friend_id。

Answer 2

无论您想要返回什么，都需要包含在查询的SELECT部分中。

尝试这样的事情：

SELECT friendpending.friend_id, 
friendpending.name, 
account.fname,
account.lname,
account.picture 
FROM account
INNER JOIN friendpending ON account.account_id = friendpending.account_id
WHERE friendpending.account_id = p_account_id;

SQL Join返回错误的结果

2 个答案: