How to write query for this scenario

Question

Hi - 
I have two table like this: 
Question: 
questionid  questiontext
1 comment
2 score
Answer:
authkey  questionid
questiontext answertext
101 1 comment hi!!
101 2 score 4
102 1 comment excellent
102 2 score 5
103 2 score 6
104 2 score 8
Here there are  two question (score and comment) and answer is stored in answer table. there are case when there is no comment and only answer. but answer would always be there in answer table for each authkey. 
I want to write the query that gives the result that if no comment is given for authkey then return null as answer. something like below: 
Desired Result: 
authkey questionid questiontext
answertext
101 1 comment hi!!
101 2 score 4
102 1 comment excellent
102 2 score 5
103 2 score 6
103 1 comment null
104 2 score 8
104 1 comment null
what query can i write to get the above desired result. 
Thanks in advance

Answer 1

Try below solution, it is NOT best solution but might work:
Declare @Questions TABLE (QuestionID INT, QuestionText Varchar(100))
INSERT INTO @Questions
VALUES (1, 'Comment'), (2, 'Score')
DECLARE @Answers TABLE (authkey INT, QuestionID INT, questiontext VARCHAR(100), answertext VARCHAR(100))
INSERT INTO @Answers
VALUES (101, 1, 'comment', 'hi!!'), (101, 2, 'score', '4'), (102, 1, 'comment', 'excellent'), (102, 2, 'score', '5'), (103, 2, 'score', '6'), (104, 2, 'score', '8')
SELECT
A.AuthKey
,Q.QuestionID
,Q.QuestionText
,A.AnswerText
FROM
@Questions Q
INNER JOIN @Answers A ON Q.QuestionID = A.QuestionID
UNION
SELECT
A.AuthKey
,Q.QuestionID
,Q.QuestionText
,Null
FROM
@Questions Q
CROSS JOIN @Answers A
WHERE
NOT EXISTS (SELECT 1 FROM @Answers SubQry WHERE SubQry.AuthKey = A.AuthKey AND SubQry.QuestionID = Q.QuestionID)
Output
AuthKey | QuestionID
| QuestionText
| AnswerText
101 | 1 | Comment | hi!!
101 | 2 | Score | 4
102 | 1 | Comment | excellent
102 | 2 | Score | 5
103 | 1 | Comment | NULL
103 | 2 | Score | 6
104 | 1 | Comment | NULL
104 | 2 | Score | 8
Best Wishes, Arbi; Please vote if you find this posting was helpful or Mark it as answered.