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  • Optimize slow ranking query

    - by Juan Pablo Califano
    I need to optimize a query for a ranking that is taking forever (the query itself works, but I know it's awful and I've just tried it with a good number of records and it gives a timeout). I'll briefly explain the model. I have 3 tables: player, team and player_team. I have players, that can belong to a team. Obvious as it sounds, players are stored in the player table and teams in team. In my app, each player can switch teams at any time, and a log has to be mantained. However, a player is considered to belong to only one team at a given time. The current team of a player is the last one he's joined. The structure of player and team is not relevant, I think. I have an id column PK in each. In player_team I have: id (PK) player_id (FK -> player.id) team_id (FK -> team.id) Now, each team is assigned a point for each player that has joined. So, now, I want to get a ranking of the first N teams with the biggest number of players. My first idea was to get first the current players from player_team (that is one record top for each player; this record must be the player's current team). I failed to find a simple way to do it (tried GROUP BY player_team.player_id HAVING player_team.id = MAX(player_team.id), but that didn't cut it. I tried a number of querys that didn't work, but managed to get this working. SELECT COUNT(*) AS total, pt.team_id, p.facebook_uid AS owner_uid, t.color FROM player_team pt JOIN player p ON (p.id = pt.player_id) JOIN team t ON (t.id = pt.team_id) WHERE pt.id IN ( SELECT max(J.id) FROM player_team J GROUP BY J.player_id ) GROUP BY pt.team_id ORDER BY total DESC LIMIT 50 As I said, it works but looks very bad and performs worse, so I'm sure there must be a better way to go. Anyone has any ideas for optimizing this? I'm using mysql, by the way. Thanks in advance Adding the explain. (Sorry, not sure how to format it properly) id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY t ALL PRIMARY NULL NULL NULL 5000 Using temporary; Using filesort 1 PRIMARY pt ref FKplayer_pt77082,FKplayer_pt265938,new_index FKplayer_pt77082 4 t.id 30 Using where 1 PRIMARY p eq_ref PRIMARY PRIMARY 4 pt.player_id 1 2 DEPENDENT SUBQUERY J index NULL new_index 8 NULL 150000 Using index

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  • Can a sql server aggregate udf be passed in multiple parameters?

    - by Burg
    I am trying to write an aggregate udf for using Sql Server 2008 and C# 3.5 that implodes an aggregation of data. The kind of syntax I am looking for is: SELECT [dbo].[Implode]([Id], ',') FROM [dbo].[Table] GROUP BY [ForeignID] where the second parameter is the delimiter for the aggregate function. And example return value would be something like: 1,4,56 Is there a way to have multiple parameters in an aggregate udf?

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  • How to write a contains statement to match a member of a class?

    - by afuzzyllama
    If I have the following structure: Public Class UserData Public ID As String Public Name As String End Class How can I select it in a conditional like this? Dim myUsers As New List(Of UserData) If myUsers.Contains(.ID = "1") = True Then ... I know that myUsers.Contains(.ID = "1") is totally wrong, but I am curious how to do something like that? Is it possible? Is this a job for LINQ?

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  • group by query issue

    - by user319088
    gorup by query issue i have one table, which has three fields and data. Name , Top , total cat , 1 ,10 dog , 2, 7 cat , 3 ,20 hourse 4, 4 cat, 5,10 Dog 6 9 i want to select record which has highest value of "total" for each Name so my result should be like this. Name , Top , total cat , 3 , 20 hourse , 4 , 4 Dog , 6 , 9 i tried group by name order by total, but it give top most record of group by result. any one can guide me , please!!!!

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  • Getting max. screen resolution with Group By

    - by Quandary
    Question: I have a website where I gather browser statistics. I have an SQL table (T_Visits), with the following columns: uniqueidentifier Visit_UID, uniqueidentifier User_UID, datetime Visit_DateTime, float Screen_w, float Screen_h, float Resolution = Screen_w * Screen_h varchar resolutionstring = screen_w + ' x ' + screen_h Now I want to get the maximum/minimum resolution each user had: Select User_UID, max(resolution) from T_Visits GROUP BY User_UID How can I get the corresponding resolution string ? I mean I can get the max(screen_w) and max(screen_h), but there's no guarantee that the corresponding resolutionstring would be max(screen_w) +' x '+ max(screen_h)

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  • how to show video or movie file into UIImagePickerController?

    - by rakesh-bhatt99
    I am using UIImagePickerController that gives user to be able select an existing photo or use the camera to take an image at that time. And i can show that image in my application with UIImageView. Now i want to use this ability for movies also. But i couldn't find any way to show the selected movie as an image in my app, just like the Photos app. as you know you can see photos and movies in the same list.

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  • Is it possible to keep mysql migration running without keeping connection open?

    - by taw
    ALTER TABLE can easily take a few days - and during this time there's a non-negligible chance of connection getting terminated due to network problems. Is it possible to start ALTER TABLE (or CREATE TABLE ... SELECT ...; or some other very long running query) and leave it running without keeping connection open all the time? (the obvious solution of screen + console mysql client won't easily work as there's no ssh running on that server, only mysqld).

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  • Multiple OR Clauses in MySQL

    - by Grant
    I'm trying to grab content where id = 3 OR id = 9 OR id = 100... Keep in mind, I can have a few hundred of these ids. What is the most efficient way to write my query? $sql = "SELECT name FROM artists WHERE (id=3 OR id=9 OR .... id-100)"

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  • Getting error using ContactManager Sample

    - by OceanBlue
    I have created some contacts data in the emulator. When I run the ContactManager sample app downloaded from the Android site, I get an error. Specifically, when trying to add a Contact through the app, I get a NullPointerException. I think it is because the "Target Accounts" spinner on the scree is not getting populated, and hence I cannot select a Target Account before adding a contact. Has anyone run across this problem or has any clues on how to fix this?

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  • Deleting Multiple rows from a TableView

    - by Sid
    hi Frnz, i want to delete multiple rows from a table view based on users selection.obviously i cant use didSelectRowAtIndexPath method coz it will be called for every row selected. i want to allow user to select multiple rows for deletion and then delete them in one go...Is it possible if yes then how to go about it.Also i am using a single view based project and i want the header of table view changed to "Delete" on the same view when the user want to delete the rows from the view. Thx

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  • SQL: Find the max record per group

    - by user319088
    I have one table, which has three fields and data. Name , Top , Total cat , 1 , 10 dog , 2 , 7 cat , 3 , 20 horse , 4 , 4 cat , 5 , 10 dog , 6 , 9 I want to select the record which has highest value of Total for each Name, so my result should be like this: Name , Top , Total cat , 3 , 20 horse , 4 , 4 Dog , 6 , 9 I tried group by name order by total, but it give top most record of group by result. Can anyone guide me, please?

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  • Linq qurery with multiple where's

    - by Dan
    I am trying the to query my Status Update repository using the following var result = (from s in _dataContext.StatusUpdates where s.Username == "friend1" && s.Username == "friend2" etc... select s).ToList(); Insead of using s.Username == "friendN" continously is there anyway I can pass a list or array or something like that rather that specifying each one, or can i use a foreach loop in the middle of the query. Thanks

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  • addAttributeToFilter and OR condition in Magento's Collection

    - by ÉricP
    Hi, I'd like to select products depending on several criteria from different attribute. I know how to user $collection->addAttributeToFilter('someattribute', array('like' => '%')); But I'd like to use several attribute for OR condition. Like: $collection->addAttributeToFilter('someattribute', array('like' => 'value'));` OR $collection->addAttributeToFilter('otherattribute', array('like' => 'value'));` To get products which either 'someattribute' OR 'otherattribute' set to 'value' Is it possible?

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  • exploratory SPARQL queries?

    - by significance
    whenever i start using sql i tend to throw a couple of exploratory statements at the database in order to understand what is avaliable, and what form the data takes. eg. show tables describe table select * from table could anyone help me understand the way to complete a similar exploration of an rdf datastore using a SPARQL endpoint? Thanks :)

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