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Get top n records for each group of grouped results
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MySQL select top X records for each individual in table
(1 answer)
Closed 3 years ago.
I have two tables Teams and Players. A Team can have an unlimited number of Players and a Player can only belong to one team.
Each Player on a team has a wage.
I would like to get the average wage of the top 16 players at each team (or the less if there are less than 16 players).
Here is an example schema:
CREATE TABLE `teams` (
`id` INT(10) UNSIGNED NOT NULL,
`name` VARCHAR(255) COLLATE utf8mb4_unicode_ci NOT NULL,
`aw16 DECIMAL(10,2) UNSIGNED DEFAULT NULL,
PRIMARY KEY (`id`),
) ENGINE=INNODB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
CREATE TABLE `players` (
`id` INT(10) UNSIGNED NOT NULL,
`name` VARCHAR(255) COLLATE utf8mb4_unicode_ci NOT NULL,
`team_id` INT(10) UNSIGNED NOT NULL,
`wage` INT(10) UNSIGNED NOT NULL,
PRIMARY KEY (`id`),
) ENGINE=INNODB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
I can get the top 16 average for one team at a time quite easily like so:
SELECT teams.name, AVG(players.wage)
FROM teams
INNER JOIN (
SELECT wage, team_id
FROM players
WHERE team_id = 1
ORDER BY wage DESC
LIMIT 16
) players
ON team_id = teams.id
GROUP BY teams.id
But I can't figure out how to do it for all Teams in one query so I can wind up with the "Team ID" and the "Top 16 Average" in two columns.
What's more I actually want to do an update and fill the aw16 field in the Teams table with the calculation for each team, but that seems even more problematic.
try this out
SELECT teams.name, AVG(players.wage)
FROM teams
INNER JOIN (
select wage, team_id
from players
where (
select count(*) from players as p
where p.team_id = players.team_id and p.wage >= players.wage
) <= 16
) players
ON team_id = teams.id
GROUP BY teams.id
Related
I've got a project where I need to get the total number of directors and films.
It should be 6 directors and 12 films in total.
However, I have 8 directors and 12 films.
CREATE TABLE `director` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(255) NOT NULL,
PRIMARY KEY (`id`)
);
INSERT INTO `director` VALUES
(1,'Roman Polanski'),
(2,'George Lucas'),
(3,'Steven Spielberg'),
(4,'Sam Mendes'),
(5,'Sofia Coppola'),
(6,'Michael Bay'),
(7,'Justin Lin'),
(8,'Francis Coppola');
CREATE TABLE `film` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`title` varchar(255) NOT NULL,
`director_id` int(11) NOT NULL,
PRIMARY KEY (`id`)
);
INSERT INTO `film` VALUES
(1,'Saw',7),
(2,'Jaw',3),
(3,'The Pianist',1),
(4,'1917',4),
(5,'Fast and Furious',7),
(6,'Star Wars',2),
(7,'ET',3),
(8,'James bond',4),
(9,'Lost in Translation',5),
(10,'Close Encounter of the Third Kind',3),
(11,'Blood',4),
(12,'Somewhere',5);
And this is the query I used:
SELECT (
SELECT COUNT(*)
FROM director
) AS directors,
(
SELECT COUNT(*)
FROM film
) AS films
FROM dual
I'm wondering if there's a way to count the director id only if it's related to the film's id?
Just count the distinct director IDs in the film table:
select
count(*) as films,
count(distinct director_id) as directors
from film
There is no need to touch the director table at all. But as an exercise you could do the following:
select count(*) as directors
from director d
where exists (
select *
from film f
where f.director_id = d.id
)
Which will count directors who have ever directed a film.
See demo on db-fiddle.com
I have four tables as follows:
CREATE TABLE IF NOT EXISTS `categories` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`name` varchar(255) NOT NULL,
PRIMARY KEY (`id`),
) ENGINE=MyISAM DEFAULT CHARSET=utf8 ;
CREATE TABLE IF NOT EXISTS `categories_friends` (
`category_id` int(10) unsigned NOT NULL,
`friend_id` int(10) unsigned NOT NULL,
UNIQUE KEY `category_id` (`friend_id`,`category_id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;
CREATE TABLE IF NOT EXISTS `friends` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`user_id` int(10) unsigned NOT NULL,
`friend_id` int(10) unsigned NOT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `user_id` (`user_id`,`friend_id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 ;
CREATE TABLE IF NOT EXISTS `ratings` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`user_id` int(10) unsigned NOT NULL,
`category_id` int(10) unsigned NOT NULL,
`title` varchar(255) NOT NULL,
`description` text NOT NULL,
`rating` tinyint(2) unsigned NOT NULL,
`public` tinyint(1) NOT NULL DEFAULT '0',
`created` datetime NOT NULL,
PRIMARY KEY (`id`),
) ENGINE=MyISAM DEFAULT CHARSET=utf8 ;
I am trying to perform the following query on those tables:
SELECT *
FROM `favred`.`ratings` AS `Rating`
INNER JOIN `favred`.`friends` AS `JFriend`
ON (`JFriend`.`friend_id` = `Rating`.`user_id`)
INNER JOIN `favred`.`categories_friends` AS `JCategoriesFriend`
ON (`JCategoriesFriend`.`category_id` = `Rating`.`category_id`
AND `JCategoriesFriend`.`friend_id` = `JFriend`.`id`)
INNER JOIN `favred`.`categories` AS `JCategory`
ON (`JCategory`.`id` = `Rating`.`category_id`
AND `JCategory`.`id` = `JCategoriesFriend`.`category_id`)
WHERE `JFriend`.`user_id` = 1
AND `Rating`.`user_id` <> 1
AND `JCategory`.`id` IN (4, 14)
GROUP BY `Rating`.`id`
The query above is not working, as it returns no results (although there is data in the tables that should return), what I'm trying to do is to find all the Ratings that were not authored by me (ID:1), but were authored by my Friends, but only if I've selected to view a specific Category for that Friend, with the resulting set being filtered by a given set of specific Categories.
The INNER JOINs loop around through Rating --> Friend --> CategoriesFreind --> Category --> back to Rating.
If I remove the additional portion of the INNER JOIN's ON clauses as follows:
SELECT *
FROM `favred`.`ratings` AS `Rating`
INNER JOIN `favred`.`friends` AS `JFriend`
ON (`JFriend`.`friend_id` = `Rating`.`user_id`)
INNER JOIN `favred`.`categories_friends` AS `JCategoriesFriend`
ON (`JCategoriesFriend`.`friend_id` = `JFriend`.`id`)
INNER JOIN `favred`.`categories` AS `JCategory`
ON (`JCategory`.`id` = `JCategoriesFriend`.`category_id`)
WHERE `JFriend`.`user_id` = 1
AND `Rating`.`user_id` <> 1
AND `JCategory`.`id` IN (4, 14)
GROUP BY `Rating`.`id`
then the query will return results, but because the INNER JOIN joining the CategoriesFriend to the Rating is not being filtered by the 'JCategory'.'id' IN (4, 14) clause, it returns all Ratings by that friend instead of filtered as it should be.
Any suggestions on how to modify my query to get it to pull the filtered results?
And I'm using CakePHP, so a query that would fit into it's unique query format would be preferred although not required.
first ,why are you use the JFriend.id, does it mean something,or is it as the same as user_id?
try this one,the same logic but it's from top to bottom ,I feel:
SELECT * FROM categories as JCategory
INNER JOIN categories_friends as JCategoriesFriend ON JCategoriesFriend.category_id = JCategory.id
INNER JOIN friends AS JFriend ON JFriend.friend_id = JCategoriesFriend.friend_id
INNER JOIN ratings AS Rating ON Rating.user_id = JFriend.friend_id
WHERE JCategory.id IN (4,14) AND JFriend.user_id = 1 AND Rating.user_id <> 1 GROUP BY Rating.id
I got one result from all the data that I made for the testing.
if it does not work also,try make some correct data,maybe the data is not right...
the testing data below:
categories: id | name (14| 141414)
categories_friends: category_id| friend_id (14| 2)
friends: id | user_id | friend_id (4| 1| 2)
ratings: id | user_id | category_id | title (2| 2| 14 | 'haha')
So I wondered if the INNER JOINs were being a little too limiting and specific in their ON clauses. So I thought that maybe a LEFT JOIN would work better...
SELECT *
FROM `favred`.`ratings` AS `Rating`
INNER JOIN `favred`.`friends` AS `JFriend`
ON (`JFriend`.`friend_id` = `Rating`.`user_id`)
LEFT JOIN `favred`.`categories_friends` AS `JCategoriesFriend`
ON (`JCategoriesFriend`.`friend_id` = `JFriend`.`id`
AND `JCategoriesFriend`.`category_id` = `Rating`.`category_id`)
WHERE `JFriend`.`user_id` = 1
AND `JRatingsUser`.`id` IS NULL
AND `Rating`.`user_id` <> 1
GROUP BY `Rating`.`id`
That query worked for me.
I did away with linking to the categories table directly, and linked indirectly through the categories_friends table which sped up the query a little bit, and everything is working great.
I have this query for example (good, it works how I want it to)
SELECT `discusComments`.`memberID`, COUNT( `discusComments`.`memberID`) AS postcount
FROM `discusComments`
GROUP BY `discusComments`.`memberID` ORDER BY postcount DESC
Example Results:
memberid postcount
3 283
6 230
9 198
Now I want to join the memberid of the discusComments table with that of the discusTopic table (because what I really want to do is only get my results from a specific GROUP, and the group id is only in the topic table and not in the comment one hence the join.
SELECT `discusComments`.`memberID`, COUNT( `discusComments`.`memberID`) AS postcount
FROM `discusComments`
LEFT JOIN `discusTopics` ON `discusComments`.`memberID` = `discusTopics`.`memberID`
GROUP BY `discusComments`.`memberID` ORDER BY postcount DESC
Example Results:
memberid postcount
3 14789
6 8678
9 6987
How can I stop this huge increase happening in the postcount? I need to preserve it as before.
Once I have this sorted I want to have some kind of line which says WHERE discusTopics.groupID = 6, for example
CREATE TABLE IF NOT EXISTS `discusComments` (
`id` bigint(255) NOT NULL auto_increment,
`topicID` bigint(255) NOT NULL,
`comment` text NOT NULL,
`timeStamp` bigint(12) NOT NULL,
`memberID` bigint(255) NOT NULL,
`thumbsUp` int(15) NOT NULL default '0',
`thumbsDown` int(15) NOT NULL default '0',
`status` int(1) NOT NULL default '1',
PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=7190 ;
.
CREATE TABLE IF NOT EXISTS `discusTopics` (
`id` bigint(255) NOT NULL auto_increment,
`groupID` bigint(255) NOT NULL,
`memberID` bigint(255) NOT NULL,
`name` varchar(255) NOT NULL,
`views` bigint(255) NOT NULL default '0',
`lastUpdated` bigint(10) NOT NULL,
PRIMARY KEY (`id`),
KEY `groupID` (`groupID`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=913 ;
SELECT `discusComments`.`memberID`, COUNT( `discusComments`.`memberID`) AS postcount
FROM `discusComments`
JOIN `discusTopics` ON `discusComments`.`topicID` = `discusTopics`.`id`
GROUP BY `discusComments`.`memberID` ORDER BY postcount DESC
Joining the topicid in both tables solved the memberID issue. Thanks #Andiry M
You need to use just JOIN not LEFT JOIN and you can add AND discusTopics.memberID = 6 after ON discusComments.memberID = discusTopics.memberID
You can use subqueries lik this
SELECT `discusComments`.`memberID`, COUNT( `discusComments`.`memberID`) AS postcount
FROM `discusComments` where `discusComments`.`memberID` in
(select distinct memberid from `discusTopics` WHERE GROUPID = 6)
If i understand your question right you do not need to use JOIN here at all. JOINs are needed in case when you have many to many relationships and you need for each value in one table select all corresponding values in another table.
But here you have many to one relationship if i got it right. Then you can simply do select from two tables like this
SELECT a.*, b.id FROM a, b WHERE a.pid = b.id
This is simple request and won't create a giant overhead as JOIN does
PS: In the future try to experiment with your queries, try to avoid JOINs especially in MySQL. They are slow and dangerous in their complexity. For 90% of cases when you want to use JOIN there is simple and much faster solution.
I have been trying to select data from multiple tables whereas I sort by the count of id's from an additional table that I have joined with a Left Join. Everything works great except for that the count gets incremented with 600something instead of one for each row.
I tried as I saw in a similar problem to put distinct inside the count statement but with the only result of freezing the database.
Tables:
CREATE TABLE IF NOT EXISTS `places` (
`PlaceId` int(10) NOT NULL AUTO_INCREMENT,
`Name` varchar(45) COLLATE utf8_unicode_ci NOT NULL,
`AreaId` int(10) NOT NULL DEFAULT '1',
PRIMARY KEY (`PlaceId`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=0;
CREATE TABLE IF NOT EXISTS `places_descriptions` (
`DescId` int(45) NOT NULL AUTO_INCREMENT,
`PlaceId` int(10) NOT NULL,
`Description` varchar(1024) COLLATE utf8_unicode_ci DEFAULT NULL,
PRIMARY KEY (`DescId`),
KEY `PlaceId` (`PlaceId`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=0;
CREATE TABLE IF NOT EXISTS `places_hits` (
`HitId` int(45) NOT NULL AUTO_INCREMENT,
`PlaceId` int(45) NOT NULL,
PRIMARY KEY (`HitId`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=0;
Query:
SELECT
p.PlaceId,
p.Name,
pd.Description,
COUNT(ph.HitId) AS numHits
FROM
places_descriptions AS pd,
places AS p
LEFT JOIN places_hits AS ph
ON (p.PlaceId = ph.PlaceId)
WHERE
(p.PlaceId = pd.PlaceId) AND
(p.AreaId = 1)
GROUP BY
p.PlaceId,
p.Name,
pd.Description
ORDER BY
numHits DESC,
p.PlaceId
LIMIT 0, 10
Any ideas? Thank you!
At first glance, your problem may be that you're cross-joining pd and p because there's no ON clause. The placeId=placeId in the where masks this problem by filtering out the rows where the join was inaccurate, but it'd be better to place that condition in the ON. The large number of rows actually existing before filtering might be throwing off the count, though I'm not sure.
Try this, to start:
SELECT
p.PlaceId,
p.Name,
pd.Description,
COUNT(ph.HitId) AS numHits
FROM
places_descriptions AS pd
INNER JOIN places AS p
ON p.PlaceId = pd.PlaceID
LEFT JOIN places_hits AS ph
ON (p.PlaceId = ph.PlaceId)
WHERE
(p.AreaId = 1)
GROUP BY
p.PlaceId,
p.Name,
pd.Description
ORDER BY
numHits DESC,
p.PlaceId
I'm trying to do a SUM and store it in another table. The SUM is simple :
SELECT award.alias_id,
SUM(award.points) AS points
FROM award
INNER JOIN achiever ON award.id = achiever.award_id
I now want to store that. I figured out how to do it on a row-by-row basis :
UPDATE aliaspoint
SET points = (SELECT SUM(award.points) AS points
FROM award
INNER JOIN achiever ON award.id = achiever.award_id
WHERE achiever.alias_id = 2000)
WHERE alias_id = 2000;
I thought something like this might work but I get:
ERROR 1111 (HY000): Invalid use of group function
UPDATE aliaspoint
INNER JOIN achiever ON aliaspoint.alias_id = achiever.alias_id
INNER JOIN award ON achiever.award_id = award.id
SET aliaspoint.points = SUM(award.points)
And some table definitions to help :
mysql> show create table aliaspoint;
| metaward_aliaspoint | CREATE TABLE `aliaspoint` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`alias_id` int(11) NOT NULL,
`points` double DEFAULT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `alias_id` (`alias_id`),
KEY `aliaspoint_points` (`points`)
) ENGINE=MyISAM AUTO_INCREMENT=932081 DEFAULT CHARSET=latin1 |
mysql> show create table achiever;
| metaward_achiever | CREATE TABLE `achiever` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`modified` datetime NOT NULL,
`created` datetime NOT NULL,
`award_id` int(11) NOT NULL,
`alias_id` int(11) NOT NULL,
`count` int(11) NOT NULL,
PRIMARY KEY (`id`),
KEY `achiever_award_id` (`award_id`),
KEY `achiever_alias_id` (`alias_id`)
) ENGINE=MyISAM AUTO_INCREMENT=87784996 DEFAULT CHARSET=utf8 |
mysql> show create table award;
| metaward_award | CREATE TABLE `award` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`points` double DEFAULT NULL,
PRIMARY KEY (`id`),
) ENGINE=MyISAM AUTO_INCREMENT=131398 DEFAULT CHARSET=utf8 |
You're missing the GROUP BY clause in:
SET points = (SELECT SUM(award.points) AS points
FROM award
INNER JOIN achiever ON award.id = achiever.award_id
WHERE achiever.alias_id = 2000)
There isn't enough information on the AWARD and ACHIEVER tables, so I recommend testing this before updating the UPDATE statement:
SELECT t.id, -- omit once confirmed data is correct
a.alias_id, -- omit once confirmed data is correct
SUM(t.points) AS points
FROM AWARD t
JOIN ACHIEVER a ON a.award_id = t.id
GROUP BY t.id, a.alias_id
Once you know the summing is correct, update the INSERT statement:
SET points = (SELECT SUM(t.points)
FROM AWARD t
JOIN ACHIEVER a ON a.award_id = t.id
WHERE a.alias_id = 2000 --don't include if you don't need it
GROUP BY t.id, a.alias_id)