Currently I am performing a left join on two tables. The first table has an id and a persons name, the second table has an id, the id of a person from table 1, and then a timestamp (of a flight).
People Flights
id | name id | person_id | time
------------ ---------------------------
1 Dave 1 1 1284762115
2 Becky 2 1 1284787352
3 2 1284772629
4 2 1286432934
5 1 1283239480
When I perform my left join, I get a list of people and their flight times, but what I would like is just the list of people with the flight time with the highest ID
I have been using
SELECT p.id, p.name max(f.time)
FROM People p
LEFT JOIN Flights f ON p.id = f.person_id
GROUP BY p.id, p.name
However, this just gives me the LAST flight time, rather than the last flight time uploaded into the system (ie, highest ID).
1 Dave 1284787352
2 Becky 1286432934
So to reiterate, I would like to see the name of the person, along with the flight time of their last UPLOADED (highest ID) flight time.
1 Dave 1283239480
2 Becky 1286432934
Use:
SELECT p.id,
p.name,
f.time
FROM PEOPLE p
JOIN FLIGHTS f ON f.person_id = p.id
JOIN (SELECT f.person_id,
MAX(f.id) AS max_id
FROM FLIGHTS f
GROUP BY f.person_id) x ON x.person_id = f.person_id
AND x.max_id = f.id
If you are using a database that supports analytics:
SELECT p.id,
p.name,
x.time
FROM PEOPLE p
JOIN (SELECT f.person_id,
f.time,
ROW_NUMBER() OVER(PARTITION BY f.person_id
ORDER BY f.id DESC) AS rk
FROM FLIGHTS f) x ON x.person_id = p.id
AND x.rk = 1
If you want people, including those without flights:
SELECT p.id,
p.name,
f.time
FROM PEOPLE p
LEFT JOIN FLIGHTS f ON f.person_id = p.id
JOIN (SELECT f.person_id,
MAX(f.id) AS max_id
FROM FLIGHTS f
GROUP BY f.person_id) x ON x.person_id = f.person_id
AND x.max_id = f.id
...and the analytic version:
SELECT p.id,
p.name,
x.time
FROM PEOPLE p
LEFT JOIN (SELECT f.person_id,
f.time,
ROW_NUMBER() OVER(PARTITION BY f.person_id
ORDER BY f.id DESC) AS rk
FROM FLIGHTS f) x ON x.person_id = p.id
AND x.rk = 1
I think you are looking for something like the below. group by the person_id and select the max id then use that list to select from the flights. This is my first thought there may be a more efficent way.
EDITED:
SELECT p.id, p.name MAX(f.time)
FROM People p
LEFT JOIN Flights f ON p.id = f.person_id
WHERE f.id in(SELECT MAX(id) FROM flights GROUP BY person_id)
Related
I am trying to solve 2 queries
Find all the actors that made more movies with Yash Chopra than any other director
Select b.number,b.actor,b.director from (select MAX(a.count) as number,a.director,a.actor from
(select count(p.PID) as count ,p.PID as actor,md.PID as director from person as p left join m_cast
as
mc on trim(p.PID)=trim(mc.PID) inner join m_director as md on trim(md.MID)=trim(mc.MID) group by
md.PID ,p.PID) as a group by a.actor) as b where b.director=(select PID from person where
Name='Yash Chopra')
report for each year the percentage of movies in that year with only female actors, and the total number of movies made that year. For example, one answer will be: 1990 31.81 13522 meaning that in 1990 there were 13,522 movies, and 31.81% had only female actors. You do not need to round your answer.
SELECT female_count.year Year,
((female_count.Total_movies_with_only_female_leads)*100)/total_count.Total Percentage FROM ((SELECT
movie.year Year,count(*) Total_movies_with_only_female_leads FROM movie WHERE NOT EXISTS ( SELECT *
FROM M_Cast,person WHERE M_Cast.mid = movie.MID and M_Cast.PID = person.PID AND person.gender='Male'
) GROUP BY movie.year) female_count, (SELECT movie.year,count(*) as Total FROM movie group by
movie.year) total_count) WHERE female_count.year=total_count.year
Unfortunately for both the queries, I am getting empty table. Can someone help me in solving these 2 queries
I wrote it using CTEs so it is more readable.
First Question:
WITH HowManyMoviesPerActorDirector AS
(select mc.pid as actorpid
,pa.name as actorname
,md.pid as directorpid
,pd.name as producername
,count(mc.MID) as numberofmovies
from m_cast as mc
inner join m_director md on md.MID=mc.MID
inner join person pa ON mc.PID=pa.PID
inner join person pd ON md.PID=pd.PID
group by mc.pid as actorpid,md.pid
)
select h.acorname
,h.producername
,h.numberofmovies
from HowManyMoviesPerActorDirector h
WHERE h.numberofmovies = (select MAX(h2.numberofmovies)
from HowManyMoviesPerActorDirector h2
where h2actorpid=h.actorpid
group by h2actorpid)
AND h.producername='Yash Chopra'
The second one:
WITH MoviesIncludingGendeflag AS
( select m.mid
,m.year
,sum(case when p.gender='female' then 0 else 1 end) as genderflag
from movie m
inner join mc_cast mc on mc.mid=m.mid
inner join person p on p.pid=mc.pid
group by m.mid,m.year
) FemaleOnlyMovies AS
( select m.year,count(m.id) as Total
from MoviesIncludingGendeflag m
where generflag=0
group by m.year
), TotalMovies AS
(
select m.year,count(m.id) as Total
from movie m
group by m.year
)
select TM.year,TM.Total,(COALESCE(FOM.Total,0)*100.0/TM.Total) as percentage
from TotalMovies TM
left join FemaleOnlyMovies FOM ON FOM.year=TM.year
**List all directors who directed 5000 movies or more, in descending order of the number of movies they directed
The use of Distinct before d.name doesnot help.
result = pd.read_sql_query("SELECT d.name,count(*) as num
FROM PERSON d, M_DIRECTOR md
WHERE d.Pid = md.Pid
GROUP BY d.Pid,d.name
HAVING COUNT(*) >= 10
order by count(*) desc
",conn)
You must use proper explicit joins between the tables and count on distinct movies:
select
p.name,
count(distinct d.mid) num
from person p
inner join m_director d on d.pid = p.pid
inner join movie m on m.mid = d.mid
group by p.pid, p.name
having num >= 10
order by num desc
Probably you have duplicate records in Person table - people with the same name but different ids. Try to group just by name and not by id
result = pd.read_sql_query("SELECT d.name,count(*) as num
FROM PERSON d, M_DIRECTOR md
WHERE d.Pid = md.Pid
GROUP BY d.name
HAVING COUNT(*) >= 10
order by count(*) desc
",conn)
I have two tables in Oracle DB
Person (
id
)
Bill (
id,
date,
amount,
person_id
)
I need to get person and amount from last bill if exist.
I trying to do it this way
SELECT
p.id,
b.amount
FROM Person p
LEFT JOIN Bill b
ON b.person_id = p.id AND b.date = (SELECT MAX(date) FROM Bill WHERE person_id = 1)
WHERE p.id = 1;
But this query works only with INNER JOIN. In case of LEFT JOIN it throws ORA-01799 a column may not be outer-joined to a subquery
How can I get amoun from the last bill using left join?
Please try the below avoiding sub query to be outer joined
SELECT
p.id,
b.amount
FROM Person p
LEFT JOIN(select * from Bill where date =
(SELECT MAX(date) FROM Bill b1 WHERE person_id = 1)) b ON b.person_id = p.id
WHERE p.id = 1;
What you are looking for is a way to tell in bills, for each person, what is the latest record, and that one is the one to join with. One way is to use row_number:
select * from person p
left join (select b.*,
row_number() over (partition by person_id order by date desc) as seq_num
from bills b) b
on p.id = b.person_id
and seq_num = 1
You cannot have a subquery inside an ON statement.
Instead you need to convert your LEFT JOIN statement into a whole subquery.
Not tested but this should work.
SELECT
p.id,
b.amount
FROM Person p
LEFT JOIN (
SELECT id FROM Bill
WHERE person_id = p.id
AND date = (SELECT date FROM Bill WHERE person_id = 1)) b
WHERE p.id = 1;
I'm not quite sure why you would want to filter for the date though.
Simply filtering for the person_id should do the trick
you should join Person and Bill to the result for max date in bill related to person_id
select Person.id, bill.amount
from Person
left join bill on bill.person_id = person.id
left join (
select person_id, max(date) as max_date
from bill
group by person_id ) t on t.person_id = Person.id and b.date = t.max_date
Hey you can do like this
SELECT
p.id,
b.amount
FROM Person p
LEFT JOIN Bill b
ON b.person_id = p.id AND b.date = (SELECT max(date) FROM Bill WHERE person_id = 1)
WHERE p.id = 1
SELECT
p.id,
b.amount
FROM Person p
LEFT JOIN Bill b
ON b.person_id = p.id
WHERE (SELECT max(date) FROM bill AS sb WHERE sb.person_id=p.id LIMIT 1)=b.date;
SELECT
p.id,
c.amount
FROM Person p
LEFT JOIN (select b.person_id as personid,b.amount as amount from Bill b where b.date1= (select max(date1) from Bill where person_id=1)) c
ON c.personid = p.id
WHERE p.id = 1;
try this
select * from person p
left join (select MAX(id) KEEP (DENSE_RANK FIRST ORDER BY date DESC)
from bills b) b
on p.id = b.person_id
I use GREATEST() function in join condition:
SELECT
p.id,
b.amount
FROM Person p
LEFT JOIN Bill b
ON b.person_id = p.id
AND b.date = GREATEST(b.date)
WHERE p.id = 1
This allows you to grab the whole row if necessary and grab the top x rows
SELECT p.id
,b.amount
FROM person p
LEFT JOIN
(
SELECT * FROM
(
SELECT date
,ROW_NUMBER() OVER (PARTITION BY person_id ORDER BY date DESC) AS row_num
FROM bill
)
WHERE row_num = 1
) b ON p.id = b.person_id
WHERE p.id = 1
;
I have a problem which I cannot resolve no matter what without using code, instead of SQL SCRIPT.
I have 2 tables
Person
ID Name Type
1 A A1
2 B A2
3 C A3
4 D A4
5 E A6
PersonHomes
HOMEID Location PurchaseDate PersonID
1 CA 20160101 1
2 CT 20160202 1
3 DT 20160101 2
4 BT 20170102 3
5 CT 20160303 1
6 CA 20160101 2
PersonID is foreign key of Person Table
There are no other rowz in the tables
So, we have to show detail of EACH person WITH home
The rule to write output is
IF Person has SINGLE entry in PersonHomes then use it
IF Person has MORE than ONE entry in PersonHomes then we have to look at purchase date, IF they are different then USE the PersonHomes ROW with OLDEST date in it. AND DELETE OTHER ROWS OF HIM
IF Person has MORE than ONE entry in PersonHomes then we have to look at purchase date, and IF DATES are SAME then USE the ROW with LOWER ID AND DELETE THE OTHER ROWS of HIM
This is very easy to do in code but using SQL it is complex
What I tried was to
WITH PERSON (
SELECT * FROM Person)
SELECT * FROM PERSON
INNER JOIN PersonHomes ON Person.ID = PersonHomes.PersonID
WHERE PersonHomes.PersonID = CASE WHEN (COUNT (*) FROM PersonHomes...)
Then I think I can write SQL function ?
I am stuck, Please help!
SAMPLE OUTPUT for PERSON A
ID NAME Type HOMEID Location PurchaseDate
1 A A1 5 CT 20160303
For PERSON B
ID NAME Type HOMEID Location PurchaseDate
1 A A2 3 DT 20160101
Aiden
It is not so easy to get desired output with SQL. we should write more than one sql queries.
First I created a temp table which consists of home details:
select PersonID, count(*) as HomeCount, count(distinct PurchaseDate) as
PurchaseDateCount, min(PurchaseDate) oldestPurchaseDate, min(HOMEID) as
LowerHomeID into #PersonHomesAbstractTable from PersonHomes group by PersonID
Then for the output of your first rule:
select p.ID, p.NAME, p.Type, ph.HOMEID, ph.Location, ph.PurchaseDate from Person p
inner join #PersonHomesAbstractTable a on p.ID = a.PersonID
inner join PersonHomes ph on p.ID = ph.PersonID
where a.HomeCount = 1
For the output of your second rule:
select p.ID, p.NAME, p.Type, ph.HOMEID, ph.Location, ph.PurchaseDate
from Person p inner join #PersonHomesAbstractTable a on p.ID = a.PersonID
inner join PersonHomes ph on p.ID = ph.PersonID and
ph.PurchaseDate = a.oldestPurchaseDate
where a.HomeCount > 1 and a.PurchaseDateCount <> 1
And finally for the output of your third rule:
select p.ID, p.NAME, p.Type, ph.HOMEID, ph.Location, ph.PurchaseDate
from Person p inner join #PersonHomesAbstractTable a on p.ID = a.PersonID
inner join PersonHomes ph on p.ID = ph.PersonID and
ph.HOMEID = a.LowerHomeID
where a.HomeCount > 1 and a.PurchaseDateCount = 1
Of course there are some other ways, but now this way is come to my mind.
If you want to delete undesired rows, you can use scripts below:
delete from PersonHomes where HOMEID in
(
select ph.HOMEID from #PersonHomesAbstractTable a
inner join PersonHomes ph on a.PersonID = ph.PersonID and
ph.PurchaseDate <> a.oldestPurchaseDate
where a.HomeCount > 1 and a.PurchaseDateCount <> 1
union
select p.HOMEID from #PersonHomesAbstractTable a
inner join PersonHomes ph on a.PersonID = ph.PersonID and
ph.HOMEID <> a.LowerHomeID
where a.HomeCount > 1 and a.PurchaseDateCount = 1
)
You seem to have a prioritization query. I would solve this using row_number():
select ph.*
from (select ph.*,
row_number() over (partition by personid
order by purchasedate asc, homeid asc
) as seqnum
from personhomes ph
) ph
where seqnum = 1;
This doesn't actually change the data in the table. Although you say delete, it seems like you just want a result set with one home per person.
This is shortest approach got by Link
;WITH cte AS
(
SELECT *, RowN = ROW_NUMBER() OVER (PARTITION BY ID ORDER BY AddressMoveDate DESC) FROM Address
)
DELETE FROM cte WHERE RowN > 1
I have PostgreSQL database and I try to print all my users (Person).
When I execute this query
-- show owners
-- sorted by maximum cars amount
SELECT p.id
FROM car c JOIN person p ON c.person_id = p.id
GROUP BY p.id
ORDER BY COUNT(p.name) ASC;
I get all owners sorted by cars amount
Output: 3 2 4 1
And all order goes wrong when I try to link owner id.
SELECT *
FROM person p
WHERE p.id IN (
SELECT p.id
FROM car c JOIN person p ON c.person_id = p.id
GROUP BY p.id
ORDER BY COUNT(p.name) ASC);
Output: 1 2 3 4 and other data
You see than order is wrong. So here is my question how can I save that order?
Instead Of subquery use join. Try this.
SELECT p.*
FROM person p
JOIN (SELECT p.id,
Count(p.NAME)cnt
FROM car c
JOIN person p
ON c.person_id = p.id
GROUP BY p.id) b
ON p.id = b.id
ORDER BY cnt ASC
Untangle the mess. Aggregate first, join later:
SELECT p.*
FROM person p
JOIN (
SELECT person_id, count(*) AS ct
FROM car
GROUP BY person_id
) c ON c.person_id = p.id
ORDER BY c.cnt;
No need to join to person twice. This should be fastest if you count most or all rows.
For a small selection, correlated subqueries are faster:
SELECT p.*
FROM person p
ORDER BY (SELECT count(*) FROM car c WHERE c.person_id = p.id)
WHERE p.id BETWEEN 10 AND 20; -- some very selective predicate
As for your original: IN takes a set on the right hand, order of elements is ignored, so ORDER BY is pointless in the subuery.