MySQL UNION只包括第一個表

Question

我需要在兩個表上執行FULL OUTER JOIN，我正試圖在MySQL中使用LEFT JOIN/RIGHT JOIN/UNION ALL技術來實現它。

這裏是原始表：

giving_totals: 
+--------------+---------------+-------------+ 
| country_iso2 | total_given | supersector | 
+--------------+---------------+-------------+ 
| AE   | 1396986989.02 |   3 | 
| AE   | 596757809.20 |   4 | 
| AE   | 551810209.87 |   5 | 
| AE   | 25898255.77 |   7 | 
| AE   |  32817.63 |   9 | 
... 
+--------------+---------------+-------------+ 

receiving_totals: 
+--------------+----------------+-------------+ 
| country_iso2 | total_received | supersector | 
+--------------+----------------+-------------+ 
| AE   | 34759000.00 |   3 | 
| AE   |  148793.82 |   7 | 
| AE   |   734.30 |   9 | 
| AF   | 6594479965.85 |   1 | 
| AF   | 2559712971.26 |   2 | 
+--------------+----------------+-------------+ 

我想結果表中有每個國家的每個超羣代碼的一個條目，即使它沒有給予或接受金錢爲扇區（這是從AidData項目數據集的情況下，任何人都很熟悉。）我想通過做一個左連接（獲得所有給予條目）和右連接（獲取所有接收條目）的聯合來完成此操作。以下是我嘗試的查詢：

SELECT g.country_iso2 AS country_iso2, g.total_given AS `total_given`,R.total_received AS `total_received`,g.supersector AS `supersector` 
FROM (`giving_totals` `g` 
LEFT JOIN `receiving_totals` `r` 
ON(((g.country_iso2 = r.country_iso2) 
AND (g.supersector = r.supersector)))) 

UNION ALL 

SELECT g.country_iso2 AS country_iso2, g.total_given AS `total_given`,R.total_received AS `total_received`,g.supersector AS `supersector` 
FROM (`giving_totals` `g` 
RIGHT JOIN `receiving_totals` `r` 
ON(((g.country_iso2 = r.country_iso2) 
AND (g.supersector = r.supersector)))) 

但是這隻返回第一個jo無論我是否先將右側或左側連接起來。我想我可能會誤解UNION的運作，因爲每個人的加入都會返回我的預期。任何幫助一如既往地受到讚賞。

Answer 1

這裏是做一個full outer join的替代方法：

SELECT driver.country_iso2 AS country_iso2, 
     g.total_given AS `total_given`, 
     R.total_received AS `total_received`, 
     driver.supersector AS `supersector` 
from ((select distinct country_iso2, supersector 
     from giving_totals 
    ) union 
     (select distinct country_iso2, supersector 
     from receiving_totals 
    ) 
    ) driver left outer join 
    giving_totals gt 
    on gt.country_iso2 = driver.country_iso2 and 
     gt.supersector = driver.country_iso2 left outer join 
    receiving_totals rt 
    on rt.country_iso2 = driver.country_iso2 and 
     rt.supersector = driver.country_iso2 

那就是，做工會作爲一個子查詢來獲取所有你感興趣的組合那麼你可以做一個left outer join到該表。

您的問題的原因是第二個查詢中的別名。你可以試試這個：

SELECT r.country_iso2 AS country_iso2, g.total_given AS `total_given`,R.total_received AS `total_received`,r.supersector AS `supersector` 
FROM (`giving_totals` `g` 
RIGHT JOIN `receiving_totals` `r` 
ON(((g.country_iso2 = r.country_iso2) 
AND (g.supersector = r.supersector)))) 

原始窗體對於這些值將具有NULL值。