Question

我想在一行中返回一名学生，这是我的选择：

select Name from student

结果：

 Name
 Emre

我的第二个选择是我的老师，但我仍然希望带一行：

select Name from teacher

结果：

Name
 John 
 Adam

我想要这个输出

 Name   1.Teacher   2.Teacher
 Emre   John        Adam

有可能在一行中完成吗？

Answer 1

很遗憾，您没有提供有关student如何与每个teacher相关联的任何详细信息，所以我假设您有一个表连接两个类似于以下内容的表：

CREATE TABLE student_teacher
    ([student_id] int, [teacher_id] int)
;

如果您有这种类型的连接表，那么您可以使用PIVOT函数来获得结果。如果每个学生的教师数量有限，那么您可以使用row_number()对查询进行硬编码，为每位学生的每个教学分配一个排序值：

select student_name, teacher1, teacher2
from
(
  select s.name student_name,
    t.name teacher_name,
    'teacher'
      + cast(row_number() over(partition by s.id
                                order by t.id) as varchar(10)) seq
  from student s
  inner join student_teacher st
    on s.id = st.student_id
  inner join teacher t
    on st.teacher_id = t.id
) d
pivot
(
  max(teacher_name)
  for seq in (teacher1, teacher2)
) piv;

见SQL Fiddle with Demo。但是，如果你有一定数量的教师，那么你将看到使用动态SQL：

DECLARE @cols AS NVARCHAR(MAX),
    @query  AS NVARCHAR(MAX)

select @cols = STUFF((SELECT distinct ', ' + QUOTENAME('teacher'
                                                       +cast(row_number() over(partition by student_id
                                                                              order by teacher_id) as varchar(10))) 
                    from student_teacher
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 
        ,1,1,'')

set @query = 'SELECT student_name,' + @cols + ' 
            from 
            (
              select s.name student_name,
                t.name teacher_name,
                ''teacher''
                  + cast(row_number() over(partition by s.id
                                            order by t.id) as varchar(10)) seq
              from student s
              inner join student_teacher st
                on s.id = st.student_id
              inner join teacher t
                on st.teacher_id = t.id
            ) x
            pivot 
            (
                max(teacher_name)
                for seq in (' + @cols + ')
            ) p '

execute sp_executesql @query;

请参阅SQL Fiddle with Demo

有没有办法重新排列选择结果列？

1 个答案: