数据，当字段A相同时，取字段B数值大的这一条数据

A	B	C
1	2	3
1	1	4
2	2	3
2	3	4

期望结果

A	B	C
1	2	3
2	3	4

 

Oracle

SELECT A, B, C
FROM (SELECT A, B, C,ROW_NUMBER() OVER (PARTITION BY A ORDER BY B DESC) AS rnFROM 表名
) 
WHERE rn = 1;

MySql

SELECT t1.A, t1.B, t1.C
FROM table_name t1
JOIN (SELECT A, MAX(C) AS max_CFROM 表名GROUP BY A
) t2 ON t1.A = t2.A AND t1.C = t2.max_C;