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我試圖從包含國家/地區代碼數據的3個不同列的表中選擇不同國家/地區代碼的列表。從包含相似數據的多列中選擇唯一值
例
Raw Desired
+-----------+-----------+-----------+ +-----------+
| country_1 | country_2 | country_3 | | countries |
+-----------+-----------+-----------+ +-----------+
| GBR | GBR | IRL | | ARG |
| DEU | FRA | CHE | | AUS |
| CHN | CHN | IND | | BRA |
| USA | CAN | MEX | | CAN |
| AUS | JAP | KOR | | CHE |
| BRA | ARG | ARG | | CHN |
| NOR | SWE | FIN | | DEU |
| GBR | FRA | GBR | | FIN |
| IRL | IRL | IRL | | FRA |
+-----------+-----------+-----------+ | GBR |
| IND |
| IRL |
| JAP |
| KOR |
| MEX |
| NOR |
| SWE |
| USA |
+-----------+
到目前爲止我來最接近的是一個像查詢:
mysql> SELECT
CONCAT(
(SELECT GROUP_CONCAT(DISTINCT country_1 ORDER BY country_1) FROM tbl),
',',
(SELECT GROUP_CONCAT(DISTINCT country_2 ORDER BY country_2) FROM tbl),
',',
(SELECT GROUP_CONCAT(DISTINCT country_3 ORDER BY country_3) FROM tbl)
) AS countries;
+-------------------------------------------------------------------------------------------------+
| countries |
+-------------------------------------------------------------------------------------------------+
| AUS,BRA,CHN,DEU,GBR,IRL,NOR,USA,ARG,CAN,CHN,FRA,GBR,IRL,JAP,SWE,ARG,CHE,FIN,GBR,IND,IRL,KOR,MEX |
+-------------------------------------------------------------------------------------------------+
但是你可以看到,仍然有重複,我不當然,我也可以讓他們成爲行。
任何幫助表示讚賞!
爲什麼'ARG'在你想要的結果集中?它不是在你的桌子上出現過兩次嗎? – 2014-10-17 14:41:54