怎么写oracle函数，使其得到如图中去重的结果？将左侧的字符串去重得到右侧中的内容

Question

怎么写oracle函数，使其得到如图中去重的结果？将左侧的字符串去重得到右侧中的内容

Answer 1

SELECT * FROM (
 SELECT 1 F1,'A' F2 FROM DUAL
 UNION ALL
 SELECT 1 F1,'B' F2 FROM DUAL
 UNION ALL
 SELECT 2 F1,'A' F2 FROM DUAL
 UNION ALL
 SELECT 2 F1,'B' F2 FROM DUAL
 UNION ALL
 SELECT 2 F1,'C' F2 FROM DUAL
 ) T
 WHERE 1=1
   AND ((F1 = 1 AND F2 IN ('A')) OR (F1 = 2 AND F2 IN ('B','C')))