mysql - 在子查询中使用别名

Question

我正在运行以下查询来获取投资组合的未平仓头寸:

SELECT SUM(trades.quantity) as total_quantity, SUM(trades.price) as total_cost, SUM(trades.price)/SUM(trades.quantity) as cost_per_share,           
trades.ticker, tickers.code
FROM (trades)
LEFT JOIN tickers
ON trades.ticker = tickers.id
GROUP BY tickers.code
HAVING total_quantity > 0
ORDER BY tickers.code

我想添加一个额外的列来显示职位的权重，即:

total_cost/SUM(total_cost) -- Dividing any given position cost by the total cost of the portfolio

由于别名不能在计算中使用，我想我需要使用子查询。我尝试了一些方法，但未能成功。

有人能解释一下吗？子查询是可行的方法吗？还有其他更好的方法吗？

Answer 1

不确定您的查询(您似乎正在对 LEFT JOINed 表中的字段进行 GROUP BY，对于未找到的匹配行，该字段可能为空)，但可能交叉联接到子查询以获取所有数据的总计价格

SELECT total_quantity, total_cost, cost_per_share, trades.ticker, tickers.code, total_cost/total_of_prices
FROM
(
    SELECT SUM(trades.quantity) as total_quantity, SUM(trades.price) as total_cost, SUM(trades.price)/SUM(trades.quantity) as cost_per_share,           
    trades.ticker, tickers.code
    FROM trades
    LEFT JOIN tickers
    ON trades.ticker = tickers.id
    GROUP BY tickers.code
    HAVING total_quantity > 0
) Sub1
CROSS JOIN
(
    SELECT SUM(price) as total_of_prices 
    FROM trades 
    WHERE quantity > 0
) Sub2
ORDER BY tickers.code