加入子查詢外的列

Question

SELECT t1.name as r_name, t1.values as r_values
FROM table as t1
JOIN (
    SELECT SUM(amount) as amount
    FROM database2.table
    WHERE ids IN (t1.values)
) as t2
WHERE t1.id = 20;

我收到一個錯誤，子查詢中的t1.values是未知列。

Answer 1

您需要重寫您的查詢並在where join條件：

SELECT t1.name as r_name, t1.values as r_values
FROM table as t1
JOIN (
    SELECT SUM(amount) as amount
    FROM database2.table
) as t2 ON t2.ids = t1.values
WHERE t1.id = 20;

另外，您不使用amount列，那么join的意義何在？

另一個問題，您沒有定義任何join條件。

我認為您需要先閱讀 SQL 中的join :)

Answer 2

您似乎正在嘗試根據t1.values列表將database2.table加入到您的t1中。 自從您使用聚合 function 以來，我在t2中添加了按 ID 分組。 然后，不確定您的sum(amount)的目的是什么

SELECT t1.name as r_name, t1.values as r_values
FROM table as t1
JOIN (
    SELECT SUM(amount) as amount, ids
    FROM database2.table
    GROUP BY ids
) as t2 on t2.ids IN (t1.values)
WHERE t1.id = 20;