輕鬆搞定左外鏈接、右外鏈接、內鏈接、全鏈接、交叉鏈接

SELECT * FROM(         SELECT '1' A,'a' B FROM dual     UNION SELECT '2','b' FROM dual     UNION SELECT '4','c' FROM dual     UNION SELECT '3','c' FROM dual ) a   // 注意這是a表 LEFT JOIN (         SELECT

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