MySql operator complexity

Question

I have a pet project on feedback system with to tables, one caputres the questions of customers and another caputures the answeers of help desk.

////////////////////////////////////////////////////////////////////////
Customers_Question table         AND   helpdesk_answers  includes: 
Qst_id(pk),                            Qst_id(pk)(FK)
qst_title,                             helpdesk_answer
qst_comment,
qst_customer_name, 
qst_date

to get answers mysql query is:

SELECT*from customers_question, helpdesk_answers
WHERE customers_qst.Qst_id = helpdesk_answers(FK Qst_id)

i get all questions that already answered. QUESTION: HOW DO I GET OR COUNT UNANSWERED QUESTION?

score 2 · Answer 1 · answered Jul 06 '14 at 00:42

2

SELECT q.* 
from customers_question q
left join helpdesk_answers a on q.Qst_id = a.Qst_id
where a.Qst_id is null

See this great explanation of joins

answered Jul 06 '14 at 00:42

juergen d

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score 0 · Accepted Answer · answered Jul 06 '14 at 00:46

0

using IS NULL ->

SELECT cq.* FROM customers_question cq 
LEFT JOIN helpdesk_answers ha 
    ON cq.Qst_id = ha.Qst_id 
WHERE ha.Qst_id IS NULL

OR

using NOT IN() ->

SELECT * FROM customers_question 
WHERE Qst_id NOT IN 
     (SELECT DISTINCT Qst_id FROM helpdesk_answers)

answered Jul 06 '14 at 00:46

Sean

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Every one out here is so amazing, u all are geeks... works like charm – PULabs Jul 08 '14 at 13:21
Glad we can help. Make sure to mark an answer as it will remove your question from the unanswered list. – Sean Jul 09 '14 at 05:47

score 0 · Answer 3 · edited May 23 '17 at 11:49

0

You can use the code given in the other answers to get the questions.

In order to count the rows returned you can see this answer.

edited May 23 '17 at 11:49

Community

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answered Jul 06 '14 at 00:47

ppp

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MySql operator complexity

3 Answers3