Question

我在查询中需要帮助，我需要为每年选择具有最长持续时间的课程名称。我的查询看起来像这样

select * 
from courses
where (cyear,duration) IN (
                          select cyear, max(duration)
                          from courses
                          group by cyear)

问题在于：(cyear,

会出现以下错误

表达de typenonbooléenspécifiéedansuncontexteoùunecondition est attendant，prèsde'，'。

Answer 1

SQL Server不支持in的元组。最合理的语法是切换到相关子查询：

select c.* 
from courses c
where c.duration = (select max(c2.duration)
                    from courses c2
                    where c2.cyear = c.cyear
                   );

Answer 2

使用Windows功能

select * 
from ( select * 
            , DENSE_RANK( ) over (partition by cyear order by duration desc) as rn
     ) tt
 where tt.rn = 1

Answer 3

或者，您可以选择EXISTS：

SELECT *
FROM courses c
WHERE EXISTS (SELECT 1
              FROM cources e
              WHERE e.cyear = c.cyear
              HAVING MAX(e.duration) = c.duration);

SQL列表中的元组

3 个答案: