query per estrarre le righe casuali da una tabella

Question

ho i seguenti 2 tabelle

Tabella 1 - Domande
contiene domande e marchi assegnati per ogni domanda

ID| Questions     | Marks 
________________________________________ 
1 | What is your name?   | 2 
2 | How old are you?    | 2 
3 | Where are you from?   | 2 
4 | What is your father's name? | 2 
5 | Explain about your project? | 5 
6 | How was the training session?| 5 

Table 2 - Formato domanda
Contiene quante domande (contare) da estrarre agito per una serie di Marks

Mark | Count 
------------- 
    2 | 2 
    5 | 1 

Voglio che le domande casuali per essere ritirati dal tavolo [Domande] come da [count] fissati nella tabella [Question_Format].

ID |  Question  
---------------------------- 
2 | How old are you?    
3 | Where are you from? 
6 | How was the training session? 

Answer 1

Ecco l'idea. Enumerare le domande per ciascun "segno" utilizzando row_number(). Quindi utilizzare questo numero sequenziale per selezionare le domande casuali:

select q.* 
from (select q.*, 
      row_number() over (partition by marks order by newid()) as seqnum 
     from questions q 
    ) q join 
    marks m 
    on q.marks = m.mark and q.seqnum <= m.count; 

Answer 2

with cte as (
    select *, row_number() over(partition by Marks order by newid()) as rn 
    from Questions 
) 
select 
    q.id, q.Questions 
from cte as q 
    inner join QuestionFormat as qf on qf.Mark = q.Marks 
where q.rn <= qf.[Count] 

sql fiddle demo

Answer 3

Si potrebbe in modo casuale ordinare le domande (per marchio), e poi hanno un non-uguaglianza unirsi su table2:

SELECT id, question 
FROM (SELECT id, question, marks, 
       ROW_NUMBER() OVER (PARTITION BY marks ORDER BY NEWID()) AS rn 
     FROM questions) q 
JOIN question_format qf ON q.marks = qf.mark AND q.rn <= qf.cnt