请解释如何使用派生表将此 SQL 表达为单个语句

Question

为了我自己的启发，我尝试在单个语句中编写此 SQL 功能，而不使用临时表。在我的一生中，如果没有出现 MySQL“错误 1248 (42000)：每个派生表必须有自己的别名”，我就无法让查询正常工作。

这是与我想要的类似的东西，尽管已经损坏了：

SELECT split.share, split.weight, split.creditor, split.debtor, share.amount, wsum.sum
FROM (
    SELECT split.share, split.weight, split.creditor, split.debtor, share.amount
    FROM ( split LEFT JOIN share ON split.share = share.id )
    WHERE debtor = 6 OR creditor = 6 )
    LEFT JOIN (
        SELECT split.share, SUM(weight) AS sum
        FROM split
        GROUP BY split.share
    ) wsum
    ON split.share = wsum.share;

这是我试图使用临时表表达的内容的工作版本：

CREATE TEMPORARY TABLE weightsum (share INT, sum INT);

INSERT INTO weightsum (share, sum)
SELECT split.share, SUM(weight) AS sum
FROM split
GROUP BY split.share;

CREATE TEMPORARY TABLE summary (share INT, weight INT, creditor INT, debtor INT, amount DECIMAL(10,2));

INSERT INTO summary (share, weight, creditor, debtor, amount)
SELECT split.share, split.weight, split.creditor, split.debtor, share.amount
FROM (split LEFT JOIN share ON split.share = share.id)
WHERE debtor = 6 OR creditor = 6;

SELECT summary.share, summary.weight, weightsum.sum, summary.creditor, summary.debtor, summary.amount, ((summary.amount / weightsum.sum) * summary.weight) AS split_amount
FROM summary LEFT JOIN weightsum
ON summary.share = weightsum.share;

感谢您的帮助。

Answer 1

试试这个：

SELECT split.share, split.weight, split.creditor, split.debtor, share.amount, wsum.sum
FROM (
    SELECT split.share, split.weight, split.creditor, split.debtor, share.amount
    FROM split 
    LEFT JOIN share 
    ON split.share = share.id
    WHERE debtor = 6 OR creditor = 6 
) As split
LEFT JOIN (
    SELECT split.share, SUM(weight) AS sum
    FROM split
    GROUP BY split.share
) wsum
ON split.share = wsum.share;

或更正确的写法：

SELECT split.share, split.weight, split.creditor, split.debtor, share.amount, wsum.sum
FROM split 
LEFT JOIN share 
ON split.share = share.id 
LEFT JOIN (
    SELECT split.share, SUM(weight) AS sum
    FROM split
    GROUP BY split.share
) wsum
ON split.share = wsum.share
WHERE split.debtor = 6 OR split.reditor = 6;