(T-)SQL 是否有一种简单的方法可以将行转换为这样的列？

Question

假设我有 3 张桌子，例如

       Questions 
========================
 id |     qtext 
========================
 1  | "What is 3 x 23?"
------------------------
 2  | "Your age?"

      Registrants
========================
 id |    name 
========================
 1  | "Jason" 
------------------------
 2  | "Subhasish"

               Answers
======================================
 registrant_id | question_id  | val 
======================================
      1        |       1      |  69
--------------------------------------
      2        |       2      |  45
--------------------------------------
      1        |       2      |  26

有没有办法从这个表中创建一个像

                  AnswersByPartner
==================================================
     Name     |   "What is 3 x 23?" | "Your age?"
==================================================
   "Jason"    |         69          |    26
--------------------------------------------------
  "Subhasish" |        NULL         |    45

Answer 1

我一直喜欢这样：

select
   R.name as Name, 
   A1.val as [What is 3 x 23?],
   A2.val as [Your age?]
from Registrants R
left join Answers A1 on R.id = A1.registrant_id and A1.question_id = 1
left join Answers A2 on R.id = A2.registrant_id and A2.question_id = 2

Answer 2

是的！给你（请检查列名是否有错别字）：

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

SET @cols = STUFF((SELECT distinct ',' + QUOTENAME(c.qtext) 
            FROM Questions c
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 
        ,1,1,'')


set @query = 'SELECT Name, ' + @cols + ' from 
            (
                select r.name, a.val,q.qtext from
                registrants r               
                inner join answers a
                on r.id = a.registrant_id
                inner join questions q
                on q.id = a.question_id
           ) x
            pivot 
            (
                 max(val)
                for qtext in (' + @cols + ')
            ) p '


execute(@query)