Please see the picture for ERROR SCREENSHOT
Table: Candidate
+-----+---------+
| id | Name |
+-----+---------+
| 1 | A |
| 2 | B |
| 3 | C |
| 4 | D |
| 5 | E |
+-----+---------+
Table: Vote
+-----+--------------+
| id | CandidateId |
+-----+--------------+
| 1 | 2 |
| 2 | 4 |
| 3 | 3 |
| 4 | 2 |
| 5 | 5 |
+-----+--------------+
id is the auto-increment primary key, CandidateId is the id appeared in Candidate table.
Write a sql to find the name of the winning candidate, the above example will return the winner B.
+------+
| Name |
+------+
| B |
+------+
Notes:
You may assume there is no tie, in other words there will be at most one winning candidate.
Why this code can't work? Just try to use without limit
SELECT c.Name AS Name
FROM Candidate AS c
JOIN
(SELECT r.CandidateId AS can, MAX(r.Total_vote) AS big
FROM (SELECT CandidateId, COUNT(id) AS Total_vote
FROM Vote
GROUP BY CandidateId) AS r) AS v
ON c.id = v.can;
In your query, here: SELECT r.CandidateId AS can, MAX(r.Total_vote) AS big
you use MAX aggregate function, without group by, which is not correct SQL.
Try:
SELECT Candidate.* FROM Candidate
JOIN (
SELECT CandidateId, COUNT(id) AS Total_vote
FROM Vote
GROUP BY CandidateId
ORDER BY COUNT(id) DESC LIMIT 1
) v
ON Candidate.id = v.CandidateId
This is a join/group by query with order by:
select c.name
from candidate c join
vote v
on v.candidateid = c.id
group by c.id, c.name
order by count(*) desc
limit 1;
SELECT c.Name AS Name
FROM Candidate AS c JOIN (SELECT r.CandidateId AS can
FROM
(SELECT CandidateId, COUNT(id) AS Total_vote
FROM Vote
GROUP BY CandidateId) AS r
WHERE r.Total_vote = (SELECT MAX(r.Total_vote) FROM (SELECT
CandidateId, COUNT(id) AS Total_vote
FROM Vote
GROUP BY CandidateId) r)) AS v
ON c.id = v.can;
This is updated code
My code has two errors. The first one is "use of an aggregate like Max requires a Group By clause if there are any non-aggregated columns in the select list", but not sure why my previous code still can run and show no error. Maybe the system add the group by function automatically when it run.
The second one is that max can't be used with Group by in this format.
Related
feedback table
-------------------------------
|rating|feedback|feedback_date|
-------------------------------
| 5 | good | 1452638788 |
| 1 | bad | 1452638900 |
| 0 | ugly | 1452750303 |
| 3 | ok | 1453903030 |
-------------------------------
desired result
average_rating | rating | feedback | feedback_date
2.25 | 3 | ok | 1453903030
Is it possible (in a single query) to select the average of one column and also one specific row from the table?
For example, i'd like to retrieve the average of the column rating and the most recent row as a whole.
I tried the following, and also with the ORDER BY direction as DSC but they both just gave me the average_rating and the first row in the table.
SELECT AVG(f.rating) AS average_rating, f.* FROM feedback f ORDER BY feedback_date ASC
SELECT * FROM feedback NATURAL JOIN (
SELECT AVG(rating), MAX(feedback_date) feedback_date FROM feedback
) t
See it on sqlfiddle.
you can do it with a sub query like this
SELECT AVG(f.rating) AS average_rating, t1.* FROM feedback f inner join (select * from feedback order by feedback_date asc limit 1 ) t1 on true
You can put a subquery in the SELECT clause, and calculate the average in the subquery.
SELECT (SELECT AVG(rating) FROM feedback) AS avg_rating, feedback.*
FROM feedback
ORDER BY feedback_date DESC
LIMIT 1
Sorry to confuse you about my title. I am building an auction system and I am having a difficulty in getting the user's winning item.
Example I have a table like this:
the columns are:
id, product_id, user_id, status, is_winner, info, bidding_price, bidding_date
here's my sql fiddle:
http://sqlfiddle.com/#!9/7097d/1
I want to get every user's item that they already win. So I need to identify if they are the last who bid in that item.
I need to filter it using a user_id.
If I do a query like this:
SELECT MAX(product_id) AS product_id FROM auction_product_bidding
WHERE user_id = 3;
it will get only the product_id that is 12 and the product_id of 9 did not get. Product ID 9 is also that last bid of the user_id 3.
Can you help me? I hope you got my point. Thanks. Sorry if my question a little bit confusing.
According to your question, seems 11 is also what you want, try this query:
SELECT apd.product_id
FROM auction_product_bidding apd
JOIN (
SELECT MAX(bidding_date) AS bidding_date, product_id
FROM auction_product_bidding
GROUP BY product_id
) t
ON apd.product_id = t.product_id
AND apd.bidding_date = t.bidding_date
WHERE apd.user_id = 3;
Check Demo Here
select id,product_id,user_id,status,is_winner,info,bidding_price,bidding_date,rank
from
( SELECT apb.*,
greatest(#rank:=if(product_id=#prodGrp,#rank+1,1),-1) as rank,
#prodGrp:=product_id as dummy
FROM auction_product_bidding apb
cross join (select #prodGrp:=-1,#rank:=0) xParams
order by product_id,bidding_date DESC
) xDerived
where user_id=3 and rank=1;
That user won 9,11,12
+----+------------+---------+--------+-----------+------+---------------+---------------------+------+
| id | product_id | user_id | status | is_winner | info | bidding_price | bidding_date | rank |
+----+------------+---------+--------+-----------+------+---------------+---------------------+------+
| 60 | 9 | 3 | | 0 | | 75000.00 | 2016-08-02 16:31:23 | 1 |
| 59 | 11 | 3 | | 0 | | 15000.00 | 2016-08-02 12:04:16 | 1 |
| 68 | 12 | 3 | | 0 | | 18000.00 | 2016-08-10 09:20:01 | 1 |
+----+------------+---------+--------+-----------+------+---------------+---------------------+------+
SELECT product_id FROM auction_product_bidding where bidding_price= any
(select max(bidding_price) from auction_product_bidding group by product_id)
and user_id='3';
select * from
(select product_id,user_id,max(bidding_price) from
(select * from auction_product_bidding order by bidding_price desc) a
group by product_id) b
where user_id=3;
Answer:
product_id user_id max(bidding_price)
9 3 75000
11 3 15000
12 3 18000
An idea could be to sort the table desc by date and select every distinct row by product_id and customer_id. Something like
SELECT DISTINCT prod_id, user_id FROM (
SELECT * FROM auction_product_bidding ORDER BY date DESC
)
You want everything that bids last in 3, is it right ?
I have two tables: contacts and client_profiles. A contact has many client_profiles, where client_profiles has foreign key contact_id:
contacts:
mysql> SELECT id,first_name, last_name FROM contacts;
+----+-------------+-----------+
| id | first_name | last_name |
+----+-------------+-----------+
| 10 | THERESA | CAMPBELL |
| 11 | donato | vig |
| 12 | fdgfdgf | gfdgfd |
| 13 | some random | contact |
+----+-------------+-----------+
4 rows in set (0.00 sec)
client_profiles:
mysql> SELECT id, contact_id, created_at FROM client_profiles;
+----+------------+---------------------+
| id | contact_id | created_at |
+----+------------+---------------------+
| 6 | 10 | 2014-10-09 17:17:43 |
| 7 | 10 | 2014-10-10 11:38:01 |
| 8 | 10 | 2014-10-10 12:20:41 |
| 9 | 10 | 2014-10-10 12:24:19 |
| 11 | 12 | 2014-10-10 12:35:32 |
+----+------------+---------------------+
I want to get the latest client_profiles for each contact. That means There should be two results. I want to use subqueries to achieve this. This is the subquery I came up with:
SELECT `client_profiles`.*
FROM `client_profiles`
INNER JOIN `contacts`
ON `contacts`.`id` = `client_profiles`.`contact_id`
WHERE (client_profiles.id =
(SELECT `client_profiles`.`id` FROM `client_profiles` ORDER BY created_at desc LIMIT 1))
However, this is only returning one result. It should return client_profiles with id 9 and 11.
What is wrong with my subquery?
It looks like you were trying to filter twice on the client_profile table, once in the JOIN/ON clause and another time in the WHERE clause.
Moving everything in the where clause looks like this:
SELECT `cp`.*
FROM `contacts`
JOIN (
SELECT
`client_profiles`.`id`,
`client_profiles`.`contact_id`,
`client_profiles`.`created_at`
FROM `client_profiles`
ORDER BY created_at DESC
LIMIT 1
) cp ON `contacts`.`id` = `cp`.`contact_id`
Tell me what you think.
Should be something like maybe:
SELECT *
FROM `client_profiles`
INNER JOIN `contacts`
ON `contacts`.`id` = `client_profiles`.`contact_id`
GROUP BY `client_profiles`.`contact_id`
ORDER BY created_at desc;
http://sqlfiddle.com/#!2/a3f21b/9
You need to prequery the client profiles table grouped by each contact.. From that, re-join to the client to get the person, then again to the client profiles table based on same contact ID, but also matching the max date from the internal prequery using max( created_at )
SELECT
c.id,
c.first_name,
c.last_name,
IDByMaxDate.maxCreate,
cp.id as clientProfileID
from
( select contact_id,
MAX( created_at ) maxCreate
from
client_profiles
group by
contact_id ) IDByMaxDate
JOIN contacts c
ON IDByMaxDate.contact_id = c.id
JOIN client_profiles cp
ON IDByMaxDate.contact_id = cp.contact_id
AND IDByMaxDate.maxCreate = cp.created_at
I have the following data:
| ID | Date | Code |
--------------------------
| 1 | 26/02/14 | 10 |
| 1 | 25/02/14 | 11 |
| 1 | 24/02/14 | 10 |
| 2 | 25/02/14 | 13 |
| 2 | 24/02/14 | 11 |
| 2 | 23/02/14 | 10 |
All I want is to group by the ID field and return the maximum value from the date field (i.e. most recent). So the final result should look like this:
| ID | Date | Code |
--------------------------
| 1 | 26/02/14 | 10 |
| 2 | 25/02/14 | 13 |
It seems though that if I want the "Code" field showing in the same query I also have to group or aggregate it as well... which makes sense because there could potentially be more than one value left on that field after the others are grouped/aggregated (even though there won't be in this case).
I thought I could handle this problem by doing the GroupBy and Max in a subquery on just those fields and then do a join on that subquery to bring in the "Code" field I don't want grouped or aggregated:
SELECT Q.ID, Q.MaxOfDate, A.Code
FROM
(SELECT B.ID, Max(B.Date) As MaxOfDate
FROM myTable As B
GROUP BY B.ID) As Q
LEFT JOIN myTable As A ON Q.ID = A.ID;
This isn't working though as it is still only giving me the original number of records I started with.
How do you do grouping and aggregation with fields you don't necessarily want grouped/aggregated?
An alternative to the answer I accepted:
SELECT Q.ID, Q.MaxOfDate, A.Code
FROM
(SELECT B.ID, Max(B.Date) As MaxOfDate
FROM myTable As B
GROUP BY B.ID) As Q
LEFT JOIN myTable As A ON (Q.ID = A.ID) AND (A.Date = Q.MaxOfDate);
Needed to do the LEFT JOIN on the Date field as well as the ID field.
If you want the CODE associated with the Max Date, you will have to use a subquery with a top 1, like this:
SELECT B.ID, Max(B.Date) As MaxOfDate,
(select top 1 C.Code
from myTable As C
where B.ID = C.ID
order by C.Date desc, C.Code) as Code
FROM myTable As B
GROUP BY B.ID
I have a movie database with a table for actors and another one for movies, I created a third table to add an actor partecipation in a movie. I added a field "star" to distinque leading actors from not leading actors.
I wish create a list order by the actors importance and so by the the total number of "stars".
SELECT a.id, a.name, COUNT( p.star ) AS star
FROM actors a
JOIN playing p, movies m
WHERE p.id_actor = a.id
AND p.id_movie = m.id
AND p.star =1
GROUP BY p.star
ORDER BY p.star DESC;
ACTORS
+----+---------+
| id | name |
+----+---------+
| 1 | actor01 |
| 2 | actor02 |
| 3 | actor03 |
+----+---------+
MOVIES
+----+----------+
| id | title |
+----+----------+
| 1 | movie01 |
| 2 | movie02 |
| 3 | movie03 |
+----+----------+
PLAYING
+----------+----------+-------+------+
| id_movie | id_actor | char | star |
+----------+----------+-------+------+
| 1 | 1 | char1 | 0 |
| 1 | 2 | char2 | 1 |
| 2 | 3 | char3 | 1 |
+----------+----------+-------+------+
I Need output Like:
+----------+--------------+
| actor | protagonist |
+----------+--------------+
| actor01 | 2 times |
| actor02 | 3 times |
+----------+--------------+
You need to fix the group by clause to group by the actor not the star column. You need to fix the order by to group by the aggregated column, not the original column:
SELECT a.id, a.name, sum( p.star = 1) AS stars
FROM actors a join playing p
on p.id_actor = a.id join
movies m
on p.id_movie = m.id
GROUP BY a.id, a.name
ORDER BY stars DESC;
Along the way, I fixed the from so it uses proper join syntax (with an on clause). And changed the query so it returns all actors, even those who have never been the star.
1.If you want to count all stars for an actor, you should group by actor but not stars.(Unless you want to count how many times an actor gets 1 star in a movie, you may not want to group by star)
2.You may want to use ON with JOIN
3.You may want to ORDER BY star but not ORDER BY p.star since you want to order by the result.
4.You may want to use SUM instead of COUNT to get the star counts.(SUM calculates the value but COUNT calculates the number. With SUM, you can set star value to whatever you want without change your sql. You can have star=2 which shows the actor is important to the movie or have star=-1, which means the actor stinks.)
You may have a look at the sql below:
SELECT a.id, a.name, SUM( p.star ) AS sum
FROM actors a
LEFT JOIN playing p ON p.id_actor = a.id
LEFT JOIN movies m ON p.id_movie = m.id
GROUP BY a.id
ORDER BY sum DESC;