PostgreSQL：如何使用連接編寫查詢？

我該如何使用連接編寫此查詢？我試圖去做，但它不起作用。PostgreSQL：如何使用連接編寫查詢？

select fund.fundname, sum(shares) as tt, (sum(shares)*price.price) as value 
from trans, fund, customer, price 
where trans.fundid = fund.fundid 
and trans.transdate = '2009-1-1' 
and price.fundid = trans.fundid 
and price.pricedate = trans.transdate 
and trans.sin = customer.sin 
and customer.name = 'Jacob' 
group by fund.fundname, price.price;

感謝

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2011-11-08 night mare

這是連接，甚至三個。可能甚至是交叉連接。你有什麼嘗試，爲什麼沒有工作？錯誤訊息？ – stefan

我想你在談論明確連接。就像你所擁有的那樣，連接只是隱含的。你會做這樣的：

SELECT fund.fundname, sum(shares) as tt, (sum(shares)*price.price) as value 
FROM trans 
JOIN fund 
ON (trans.fundid = fund.fundid) 
JOIN customer 
ON (trans.sin = customer.sin) 
JOIN price 
ON (price.fundid = trans.fundid) 
WHERE trans.transdate = '2009-1-1' 
AND price.pricedate = trans.transdate 
AND customer.name = 'Jacob' 
GROUP BY fund.fundname, price.price;

PostgreSQL的還允許USING一個漂亮的簡寫，這將只包括在最終的結果集中列的一個副本：

SELECT fundname, sum(shares) as tt, (sum(shares)*price.price) as value 
FROM trans 
JOIN fund 
USING (fundid) 
JOIN customer 
USING (sin) 
JOIN price 
USING (fundid) 
WHERE trans.transdate = '2009-1-1' 
AND price.pricedate = trans.transdate 
AND customer.name = 'Jacob' 
GROUP BY fund.fundname, price.price;

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2011-11-08 23:59:17

謝謝..我試圖對它進行自然連接。常規連接和自然連接有區別嗎？我的語法錯了，我相信...... –

'NATURAL' JOINS將加入每個相似命名的列。 –

天然連接沒有什麼自然的。 – stefan

你一定要分開連接條件和篩選條件：

SELECT fund.fundname, SUM(shares) AS tt, SUM(shares) * price.price AS value 
FROM trans 
INNER JOIN fund 
    USING (fundid) 
INNER JOIN price 
    ON price.fundid = trans.fundid 
    AND price.pricedate = trans.transdate 
INNER JOIN customer 
    USING (sin) 
WHERE transdate = '2009-1-1' 
    AND customer.name = 'Jacob' 
GROUP BY fund.fundname, price.price

請注意，USING會「合併」兩列，因此您不必使用別名。

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2011-11-09 00:00:20

select fund.fundname, sum(shares) as tt, (sum(shares)*price.price) as value 
from trans 
join fund on fund.fundid=trans.fundid 
join customer on customer.sin=trans.sin 
join price on price.pricedate=trans.transdate 
where 
trans.transdate = '2009-1-1' 
and customer.name = 'Jacob' 
group by fund.fundname, price.price;

來源

2011-11-09 00:01:22 Icarus

還有一個：

SELECT f.fundname 
     ,sum(shares) AS tt 
     ,(sum(shares) * p.price) AS value 
FROM trans t 
JOIN fund f USING (fundid) 
JOIN price p ON (p.fundid, p.pricedate) = (t.fundid, t.transdate) 
JOIN customer c USING (sin) 
WHERE t.transdate = '2009-1-1' 
AND c.name = 'Jacob' 
GROUP BY 1, p.price;

我使用了一些語法簡化：

USING如果左，右功能相同的名稱。小心，如果該名稱彈出多次，那麼JOINS的順序會有所不同，或者它可能會變得模糊不清。示例：sin。如果還有fund.sin，則必須改爲使用顯式JOIN ON。
(p.fundid, p.pricedate) = (t.fundid, t.transdate)是短期的
(p.fundid = t.fundid AND p.pricedate = t.transdate)
GROUP BY 1 IST簡稱
GROUP BY <fist column in the select list>

更多有關fine manual here連接。

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2011-11-09 00:30:00

PostgreSQL：如何使用連接編寫查詢？

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