I attempted the 1407. Top Travellers. But am struggling with my Oracle query below, 'Runtime error'. A little too tired to understand why. Any idea where I am going wrong? Have been rusty with SQL of late. :(
select name as name,
case when rides.distance is null then 0 else sum(rides.distance) end as travelled_distance
from users
left join rides
on users.id = rides.user_id
group by rides.users_id
order by travelled_distance desc, name;
As commented, is another way round:
select
name,
sum(case when rides.distance is null then 0 else rides.distance end) as travelled_distance
from users left join rides on users.id = rides.user_id
group by name
order by travelled_distance desc, name;
Or, simpler, use the nvl function:
select
name,
sum(nvl(rides.distance, 0)) as travelled_distance
from ...
Though, a few more objections:
you should use table aliases (as they simplify query and improve readability)
moreover, you should precede all column names with table aliases; in your case, you failed to do so for the name column. It probably belongs to the users table, but we can't tell for sure as we don't have your data model nor access to your database
group by clause should contain column(s) that aren't aggregated. In your query, that's the name column. You can put rides.users_id into that clause, but you must put name in there
The below solution works. Thanks to one of the Discussion posts at leetcode I could figure out the issue:
select r.name,
case when x.td is null
then 0
else x.td
end travelled_distance
from Users r
left join
(
select user_id, sum(distance) td
from Rides
group by user_id
) x
on r.id = x.user_id
order by travelled_distance desc, r.name;
Related
I have 3 sub-tables of different formats joined together with unions if this affects anything into full-table. There I have columns "location", "amount" and "time". Then to keep generality for my later needs I union full-table with location-table that has all possible "location" values and other fields are null into master-table.
I query master-table,
select location, sum(amount)
from master-table
where (time...)
group by location
However some "location" values are dropped because sum(amount) is 0 for those "location"s but I really want to have full list of those "location"s for my further steps.
Alternative would be to use HAVING clause but from what I understand HAVING is impossible here because i filter on "time" while grouping on "location" and I would need to add "time" in grouping which destroys the purpose. Keep in mind that the goal here is to get sum(amount) in each "location"
select location, sum(amount)
from master-table
group by location, time
having (time...)
To view the output:
with the first code I get
loc1, 5
loc3, 10
loc6, 1
but I want to get
loc1, 5
loc2, 0
loc3, 10
loc4, 0
loc5, 0
loc6, 1
Any suggestions on what can be done with this structure of master-table? Alternative solution to which I have no idea how to code would be to add numbers from the first query result to location-table (as a query, not actual table) with the final result query that I've posted above.
What you want will require a complete list of locations, then a left-outer join using that table and your calculated values, and IsNull (for tsql) to ensure you see the 0s you expect. You can do this with some CTEs, which I find valuable for clarity during development, or you can work on "putting it all together" in a more traditional SELECT...FROM... statement. The CTE approach might look like this:
WITH loc AS (
SELECT DISTINCT LocationID
FROM location_table
), summary_data as (
SELECT LocationID, SUM(amount) AS location_sum
FROM master-table
GROUP BY LocationID
)
SELECT loc.LocationID, IsNull(location_sum,0) AS location_sum
FROM loc
LEFT OUTER JOIN summary_data ON loc.LocationID = summary_data.LocationID
See if that gets you a step or two closer to the results you're looking for.
I can think of 2 options:
You could move the WHERE to a CASE WHEN construction:
-- Option 1
select
location,
sum(CASE WHEN time <'16:00' THEN amount ELSE 0 END)
from master_table
group by location
Or you could JOIN with the possible values of location (which is my first ever RIGHT JOIN in a very long time 😉):
-- Option 2
select
x.location,
sum(CASE WHEN m.time <'16:00' THEN m.amount ELSE 0 END)
from master_table m
right join (select distinct location from master_table) x ON x.location = m.location
group by x.location
see: DBFIDDLE
The version using T-SQL without CTEs would be:
SELECT l.location ,
ISNULL(m.location_sum, 0) as location_sum
FROM master-table l
LEFT JOIN (
SELECT location,
SUM(amount) as location_sum
FROM master-table
WHERE (time ... )
GROUP BY location
) m ON l.location = m.location
This assumes that you still have your initial UNION in place that ensures that master-table has all possible locations included.
It is the where clause that excludes some locations. To ensure you retain every location you could introduce "conditional aggregation" instead of using the where clause: e.g.
select location, sum(case when (time...) then amount else 0 end) as location_sum
from master-table
group by location
i.e. instead of excluding some rows from the result, place the conditions inside the sum function that equate to the conditions you would have used in the where clause. If those conditions are true, then it will aggregate the amount, but if the conditions evaluate to false then 0 is summed, but the location is retained in the result.
I cannot solve a problem with my GROUP BY problem in my query containing CASE...WHEN
Could you help me please with that?
select ID,
CODE,
NOM AS TITLE,
level,
ID_PARENT,
CASE ID_PARENT
WHEN 1111 THEN 'MAIN'
ELSE
(
SUBSTR(
(
SELECT CODE FROM units o
INNER JOIN LIB_UNITS_MV oLab on oLab.ID = o.ID WHERE o.ID = units.ID_PARENT AND LNG_CD = 'ENG'
)
, 7)
)
END AS "PARENT_CODE"
from units
INNER JOIN LIB_UNITS_MV orgLab on orgLab.ID = units.ID
WHERE orgLab.LNG ='ENG'
start with units.id = 1111
connect by prior u.ID = u.ID_PARENT
GROUP BY ID, CODE, NOM, level, ID_PARENT
I obtain the error "not a GROUP BY expression" because I have the WHEN...CASE
Thank you in advance for your help
Regards
Becuase when you group by you need to group by sufficient number of columns, which you use in select statement, outside aggregating functions (min, max, sum etc). So in your case this means - you can either group by all columns used in your case statement, or group by the whole case statement (just copy it over to your group by), or any set of sub-combinations of the whole case, altogether covering it completely. However - since you are not using any aggregate functions I would just do distinct and drop group by altogether.
When I run the script below, I got a error message "Cannot perform an aggregate function on an expression containing an aggregate or a subquery" Please provide some advice. Thanks
SELECT
CONVERT(DECIMAL(18,5),SUM(CASE WHEN PATIENT_ACCOUNT_NO IN (
SELECT PATIENT_ACCOUNT_NO
FROM STND_ENCOUNTER
GROUP BY PATIENT_ACCOUNT_NO
HAVING ( COUNT(PATIENT_ACCOUNT_NO) > 1)) THEN 0 ELSE 1 END)) dupPatNo
FROM [DBO].[STND_ENCOUNTER]
I think the error message is pretty clear. You have a sum() function with a subquery in it (albeit within a case, but that doesn't matter).
It seems that you want to choose patients that have more than one encounter, then add 0 if the patients is in the list and 1 if the patient is not. Hmmm. . . sounds like you want to count the number of patients with only one encounter.
Try using this logic instead:
select count(*)
from (select se.*, count(*) over (partition by PATIENT_ACCOUNT_NO) as NumEncounters
from dbo.stnd_encounter se
) se
where NumEncounters = 1;
As a note, the variable you are assigning is called DupPatientNo. This sounds like the number of patients that have duplicates. In that case, the query is:
select count(distinct PATIENT_ACCOUNT_NO)
from (select se.*, count(*) over (partition by PATIENT_ACCOUNT_NO) as NumEncounters
from dbo.stnd_encounter se
) se
where NumEncounters > 1;
(Or use count(*) if you want the number of encounters on duplicate patients.)
If you want to find number of PATIENT_ACCOUNT_NO that does not have any duplicates then use the following
SELECT COUNT(DISTINCT dupPatNo.PATIENT_ACCOUNT_NO)
FROM (
SELECT PATIENT_ACCOUNT_NO
FROM STND_ENCOUNTER
GROUP BY PATIENT_ACCOUNT_NO
HAVING COUNT(PATIENT_ACCOUNT_NO) = 1
) dupPatNo
If you want to find number of PATIENT_ACCOUNT_NO that have atleast one duplicate then use the following
SELECT COUNT(DISTINCT dupPatNo.PATIENT_ACCOUNT_NO)
FROM (
SELECT PATIENT_ACCOUNT_NO
FROM STND_ENCOUNTER
GROUP BY PATIENT_ACCOUNT_NO
HAVING COUNT(PATIENT_ACCOUNT_NO) > 1
) dupPatNo
Use of DISTINCT will make the query not count same item again and again
Though your query looks for first result, its not clear what you want. Hence giving query for both
I want to have a switch case in my SQL query such that when the group by does not group any element i dont want to aggregate otherwise I want to. Is that possible.
my query is something like this:
select count(1),AVG(student_mark) ,case when Count(1)=1 then student_subjectid else null end from Students
group by student_id
i get this error Column 'student_subjectid' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.
Thanks in advance..
SELECT
student_id,
COUNT(*) AS MarkCount,
AVG(student_mark) AS student_mark,
CASE COUNT(*) WHEN 1 THEN MIN(student_subjectid) END AS student_subjectid
FROM Students
GROUP BY student_id
Why in the world would you complicate it?
select count(1), AVG(Student_mark) Student_mark
from Students
group by student_id
If there is only one student_mark, it is also the SUM, AVG, MIN and MAX - so just continue to use the aggregate!
EDIT
The dataset that would eventuate with your requirement will not normally make sense. The way to achieve that would be to merge (union) two different results
select
numRecords,
Student_mark,
case when numRecords = 1 then student_subjectid end # else is implicitly NULL
from
(
select
count(1) AS numRecords,
AVG(Student_mark) Student_mark,
min(student_subjectid) as student_subjectid
from Students
group by student_id
) x
i have a trivia game and i want to reward users for 2 events:
1) answering correctly
2) sending a question to the questions pool
i want to query for score and rank of a specific player and i use this query:
SELECT (correct*10+sent*30) AS score, #rank:=#rank+1 AS rank
FROM ( trivia_players
JOIN ( SELECT COUNT(*) AS sent, senderid
FROM trivia_questions
WHERE senderid='$userid'
) a
ON trivia_players.userid=a.senderid
)
ORDER BY score DESC
and it works if the player is in both tables i.e answered correctly AND sent a question.
but it doesn't work if a player hasn't sent a question
any idea how to fix this query? ($userid is the given parameter)
thanks!
Thanks Tom! only problem is the ranks are not correct:
userid score rank
58217 380 1
12354 80 3
32324 0 2
I would probably do it like this:
SELECT
user_id,
score,
rank
FROM
(
SELECT
TP.user_id,
(TP.correct * 10) + (COUNT(TQ.sender_id) * 30) AS score,
#rank:=#rank + 1 AS rank
FROM
Trivia_Players TP
LEFT OUTER JOIN Trivia_Questions TQ ON
TQ.sender_id = TP.user_id
GROUP BY
TP.user_id,
TP.correct
ORDER BY
score DESC
) AS SQ
WHERE
SQ.user_id = $user_id
I don't use MySQL much, so the syntax may not be perfect. I think that you can use a subquery like this in MySQL. Assuming that MySQL handles COUNT() by only counting rows with a non-null value for , this should work.
The keys are that you do a COUNT over a non-null column from Trivia Questions so that it counts them up by the user and you need to use a subquery so that you can get ranks for everyone BEFORE constraining to a particular user id.
Have you tried using a RIGHT JOIN or LEFT JOIN? Just off the top of my head!