Question

--------------------------------------------------------------
AnimalName  AnimalType  RowNumber   
---------------------------------------------------------------
Chicken         Bird        1   
Duck            Bird        2       
Alpaca          Mammal      1   
Camel           Mammal      2   
Carabao         Mammal      3   
Whale           Sea         1   
Shark           sea         2   
Prawns          Sea         3   
Eel             sea         4

输出

AnimalName      AnimalType  RowNumber   
------------------------------------------------------------        
Duck              Bird          2   
Carabao           Mammal        3   
Eel               sea           4

查询：

  SELECT t.* from (
select  
    AnimalName,
    AnimalType,
    ROW_NUMBER() OVER(PARTITION BY AnimalType ORDER BY AnimalName) AS RowNumber
FROM    Animal A
) t
where rownumber=1

上面的查询给了我所有的第一个rownumber，如果我想选择最后一个rownumber，那么我必须做出什么改变。例如：bird max rownumber为2，哺乳动物max为3，sea max为4

Answer 1

只需使用DESC代替ASC ORDER BY：

SELECT a.* 
FROM (SELECT AnimalName, AnimalType,
             ROW_NUMBER() OVER (PARTITION BY AnimalType ORDER BY AnimalName DESC) AS RowNumber
      FROM Animal a
     ) a
WHERE rownumber = 1;

如果您确实要保留行号，请使用COUNT(*)进行比较：

SELECT a.AnimalName, a.AnimalType, a.rownumber
FROM (SELECT AnimalName, AnimalType,
             ROW_NUMBER() OVER (PARTITION BY AnimalType ORDER BY AnimalName) AS RowNumber,
             COUNT(*) OVER (PARTITION BY AnimalType) as cnt
      FROM Animal a
     ) a
WHERE rownumber = cnt;

需要选择最后

1 个答案: