减去行返回更新表sql

Question

我对更复杂的SQL很新，并且无法正确更新此代码

$sql = "UPDATE bank_accounts
    SET bank_accounts.balance = bank_accounts.balance - upgrades.cost 
    FROM upgrades
    INNER JOIN upgrades AS u
    WHERE u.id = :id
    AND
    bank_accounts.uid = :uid"

;

Answer 1

一些事情......

1. ：id和：uid来自哪里？
2. 如果您将升级别名为'u'，那么您始终必须使用'u'，因此您无法输入'upgrades.cost'。它应该是'u.cost'。
3. 您还在FROM子句中列出了两次“升级”。

试试这个吗？

$sql = "UPDATE bank_accounts
          SET bank_accounts.balance = bank_accounts.balance - u.cost 
        FROM upgrades u INNER JOIN bank_accounts
             ON u.id = back_accounts.id";

另一个想法...... 更新让我感到紧张，所以我总是喜欢在进行更新之前对数据进行SELECT。

SELECT bank_accounts.balance as BEFORE, bank_accounts.balance - u.cost as AFTER
FROM bank_accounts, upgrades u
     ON u.id = bank_accounts.id