I want to know how many users answerd a question, so I made that query :
SELECT answer.idAnswer,
answer.title,
answercategory.label,
(SUM(1)) as nbAnswer
FROM ANSWER
INNER JOIN answerCategory ON answer.idAnswerCategory = answercategory.idAnswerCategory
LEFT JOIN answerUser ON answer.idAnswer = answerUser.idAnswer
GROUP BY answer.idAnswer
Its almost working, the only thing that doesn't work is that it's giving me "one" answer if nobody answered the question (it means even if there are no records in answerUser). I would like to have zero instead of one in that case. If I add a "-1", when there is one answer, I'll get zero. Any idea how I can correct that?
Use COUNT(answerUser.idAnswer) instead of SUM(1). Count will ignore the NULL rows created by the LEFT JOIN.
Use COUNT(*) instead of SUM(1).
SELECT answer.idAnswer, answer.title, answercategory.label, count(*) as nbAnswer
FROM answer
INNER JOIN answerCategory on answer.idAnswerCategory = answercategory.idAnswerCategory
LEFT JOIN answerUser ON answer.idAnswer = answerUser.idAnswer
GROUP BY answer.idAnswer
Related
this query return result of all row with P500 & S500, except that the prj_end_dt won't work at all it simply ignore it is there a way to make it work?
thank you,
SELECT project_labour.cod_no,project.prj_no,project.prj_end_dt,project_labour.pla_hrs_budg
FROM project_labour
FULL OUTER JOIN project ON project_labour.prj_no=project.prj_no
WHERE project_labour.cod_no='S500' OR project_labour.cod_no='P500' AND prj_end_dt<'2019-01-01'
FULL JOIN is almost never necessary. I rarely use it, and I write lots of queries. Filtering is even more troublesome. I am guessing that you really want:
SELECT pl.cod_no, p.prj_no, p.prj_end_dt, pl.pla_hrs_budg
FROM project p LEFT JOIN
project_labour pl
ON pl.prj_no = p.prj_no AND pl.cod_no IN ('S500', 'P500')
WHERE p.prj_end_dt < '2019-01-01';
This will return all projects from prior to 2019. Any matching project_labour rows will be returned. If there are none, then those columns will be NULL. It is quite possible that an INNER JOIN is sufficient for the query; the IN condition fixes the problem with your logic.
I have a practice question that I am struggling with.
Here are:
image of the table
my code and the answer i get
the answer im SUPPOSED to get
Thanks.
As far as I understand, you get the TeachersAnswers result from the query.
I think that you may use the below query instead of yours :
SELECT horse_name, COUNT(place)
from horse h
left join entry e on e.horse_id = h.horse_id
where e.place = 1
group by horse_name
I made a query and wanted to not have any duplicates but i got some times 3 duplicates and when i used DISTINCT or DISTINCTROW i got only 2 duplicates.
SELECT f.flight_code,
f.status,
a.airport_name,
a1.airport_name,
f.departing_date+f.departing_time AS SupposedDepartingTime,
f.landing_date+f.landing_time AS SupposedLandingTime,
de.actual_takeoff_date+de.actual_takeoff_time AS ActualDepartingTime,
SupposedLandingTime+(ActualDepartingTime-SupposedDepartingTime) AS ActualLandingTime
FROM
(((Flights AS f
LEFT JOIN Aireports AS a
ON a.airport_code = f.depart_ap)
LEFT JOIN Aireports AS a1
ON f.target_ap = a1.airport_code)
LEFT JOIN Irregular_Events AS ie
ON f.flight_code = ie.flight_code)
LEFT JOIN Delay_Event AS de
ON ie.IE_code = de.delay_code;
had to use LEFT JOIN because when i used INNER JOIN i missed some of the things i wanted to show because i wanted to see all the flights and not only the flights that got delayed or canceled.
This is the results when i used INNER JOIN, you can see only the flights that have the status "ביטול" or "עיכוב" and that is not what i wanted.
[the results with LEFT JOIN][2]
[2]: https://i.stack.imgur.com/cgE2G.png
and when i used DISTINCT where you see the rows with the NUMBER 6 on the first column it appear only two times
IMPORTANT!
I just checked my query and all the tables i use there and i saw my problem but dont know how to fix it!
in the table Irregular_Events i have more the one event for flights 3,6 and 8 and that is why when i use LEFT JOIN i see more even thou i use distinct, please give me some help!
Not entirely sure without seeing the table structure, but this might work:
SELECT f.flight_code,
f.status,
a.airport_name,
a1.airport_name,
f.departing_date+f.departing_time AS SupposedDepartingTime,
f.landing_date+f.landing_time AS SupposedLandingTime,
de.actual_takeoff_date+de.actual_takeoff_time AS ActualDepartingTime,
SupposedLandingTime+(ActualDepartingTime-SupposedDepartingTime) AS ActualLandingTime
FROM
((Flights AS f
LEFT JOIN Aireports AS a
ON a.airport_code = f.depart_ap)
LEFT JOIN Aireports AS a1
ON f.target_ap = a1.airport_code)
LEFT JOIN
(
SELECT
ie.flight_code,
de1.actual_takeoff_date,
de1.actual_takeoff_time
FROM
Irregular_Events ie
INNER JOIN Event AS de1
ON ie.IE_code = de1.delay_code
) AS de
ON f.flight_code = de.flight_code
It is hard to tell what is the problem with your query without any sample of the output, and without any description of the structure of your tables.
But your problem is that your are querying from the flights table, which [I assume] can be linked to multiple irregular_events, which can possibly also be linked to multiple delay_event.
If you want to get only one row per flight, you need to make sure your joins return only one row too. Maybe you can do it by adding one more condition to the join, or by adding a condition in a sub-query.
EDIT
You could try to add a GROUP BY to the query:
GROUP BY
f.flight_code,
f.status,
a.airport_name,
a1.airport_name;
I have tow tables 'matches' and 'forum' I need to get match information from the matches table which has comments in the forum table so I use the following query:
SELECT distinct forum.match_static_id, matches.*
from forum
INNER JOIN matches
ON forum.match_static_id = matches.static_id
WHERE forum.comments_yes_or_no = 1
I use distinct to avoid getting the same match twice if it has more than one comment in the forum table.
The problem is I want to get the count of each match comments with the same query is it possible? I use :
SELECT distinct forum.match_static_id, count(forum.comments), matches.*
from forum
INNER JOIN matches
ON forum.match_static_id = matches.static_i
WHERE forum.comments_yes_or_no = 1
but it give me just one record (which is wrong). What is the problem ?? does I need to use group by ? and if yes where to but it in this crowded query?
Please try this:
SELECT forum.match_static_id, count(matches.id), matches.*
from forum
INNER JOIN matches
ON forum.match_static_id = matches.static_i
WHERE forum.comments_yes_or_no = 1
GROUP BY forum.id
LEFT JOIN PatientClinics AB ON PPhy.PatientID = AB.PatientID
JOIN Clinics CL ON CL.ID = AB.ClinicID
AND COUNT(AB.ClinicID) = 1
I get error using Count(AB.ClinicID) = 1 (ClinicID has duplicate values in the table and
I want to use only 1 value of each duplicate value of ClinicId to produce result)
What mistake am I making?
I've never seen a COUNT() being used in a JOIN before. Maybe you should use:
HAVING COUNT(AB.ClinicID) = 1
instead.
Count() can't be used as a join/filter predicate. It can be used in the HAVING clause however. You should include the entire query in order to get a better example of how to rewrite it.
maybe investigate the HAVING clause instead of using COUNT where you put it.
hard to help without the full query.