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  • Join using combined conditions on one join table

    - by Nathan Wienert
    I have join a table joining songs to genres. The table has a 'source' column that's used to identify where the genre was found. Genres are found from blogs, artists, tags, and posts. So, songs | song_genre | genres id | song_id, source, genre_id | id What I want to build is a song SELECT query that works something like this, given I already have a genre_id: IF exists song_genre with source='artist' AND a song_genre with source='blog' OR exists song_genre with source='artist' AND a song_genre with source='post' OR exists song_genre with source='tag' I'm was going to do it by doing a bunch of joins, but am sure I'm not doing it very well. Using Postgres 9.1.

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  • How to avoid geometric slowdown with large Linq transactions?

    - by Shaul
    I've written some really nice, funky libraries for use in LinqToSql. (Some day when I have time to think about it I might make it open source... :) ) Anyway, I'm not sure if this is related to my libraries or not, but I've discovered that when I have a large number of changed objects in one transaction, and then call DataContext.GetChangeSet(), things start getting reaalllly slooowwwww. When I break into the code, I find that my program is spinning its wheels doing an awful lot of Equals() comparisons between the objects in the change set. I can't guarantee this is true, but I suspect that if there are n objects in the change set, then the call to GetChangeSet() is causing every object to be compared to every other object for equivalence, i.e. at best (n^2-n)/2 calls to Equals()... Yes, of course I could commit each object separately, but that kinda defeats the purpose of transactions. And in the program I'm writing, I could have a batch job containing 100,000 separate items, that all need to be committed together. Around 5 billion comparisons there. So the question is: (1) is my assessment of the situation correct? Do you get this behavior in pure, textbook LinqToSql, or is this something my libraries are doing? And (2) is there a standard/reasonable workaround so that I can create my batch without making the program geometrically slower with every extra object in the change set?

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  • 2-column table with two foreign keys. Performance/design question.

    - by Emanuel
    Hello everyone! I recently ran into a quite complex problem and after looking around a lot I couldn't find a solution to it. I've found answers to my questions many times before on stackoverflow.com, so I decided to post here. So I'm making a user/group managment system for a web-based project, and I'm storing all related data into a postgreSQL database. This system relies on three tables: USERS GROUPS GROUP_USERS The two first tables simply define all the users and all the groups on the site, and the last table, GROUP_USERS, stores the groups every user is part of. It only has two columns: USER_ID GROUP_ID Since every user can be a member of several groups, I decided to make a separate table for this purpose, rather than storing a comma separated column in the USERS-table. Now, both columns are foreign keys, and I want to make them both primary keys as well, this since each combination of USER_ID and GROUP_ID has to be unique, and if I give them the constraint UNIQUE pgAdmin tells me that each table should have at least one Primary key. But now I am stuck with what seems to be a lot of indexes and relations to a very small table only containing numbers. In the end, I want this table to be as fast as possible, even if containing tens of thousands of rows. Size on disk shouldn't be a problem since its just all numbers anyway, but it feels quite stupid to have a full-sized index refering to a smaller table. Should I stick with my current solution, store comma-separated values in a column in the USERS-table or is there any other solution I should be aware of. PS. I don't want to use an array-column, even if they are supported by postgreSQL. I want to be as generic as possible so I can switch database later on, if necessary. EDIT: I other words, will using a compound primary key and two foreign keys in one table with only two columns have a negative impact on performance rather than the opposite due to the size of the generated index? Thank you!

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  • Get count matches in query on large table very slow

    - by Roy Roes
    I have a mysql table "items" with 2 integer fields: seid and tiid The table has about 35000000 records, so it's very large. seid tiid ----------- 1 1 2 2 2 3 2 4 3 4 4 1 4 2 The table has a primary key on both fields, an index on seid and an index on tiid. Someone types in 1 or more tiid values and now I would like to get the seid with most results. For example when someone types 1,2,3, I would like to get seid 2 and 4 as result. They both have 2 matches on the tiid values. My query so far: SELECT COUNT(*) as c, seid FROM items WHERE tiid IN (1,2,3) GROUP BY seid HAVING c = (SELECT COUNT(*) as c, seid FROM items WHERE tiid IN (1,2,3) GROUP BY seid ORDER BY c DESC LIMIT 1) But this query is extremly slow, because of the large table. Does anyone know how to construct a better query for this purpose?

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  • Performing Inner Join for Multiple Columns in the Same Table

    - by frankiefrank
    I have a scenario which I'm a bit stuck on. Let's say I have a survey about colors, and I have one table for the color data, and another for people's answers. tbColors color_code , color_name 1 , 'blue' 2 , 'green' 3 , 'yellow' 4 , 'red' tbAnswers answer_id , favorite_color , least_favorite_color , color_im_allergic_to 1 , 1 , 2 3 2 , 3 , 1 4 3 , 1 , 1 2 4 , 2 , 3 4 For display I want to write a SELECT that presents the answers table but using the color_name column from tbColors. I understand the "most stupid" way to do it naming tbColors three times in the FROM section, using a different alias for each column to replace. How would a non-stupid way look?

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  • While Loop in TSQL with Sum totals

    - by RPS
    I have the following TSQL Statement, I am trying to figure out how I can keep getting the results (100 rows at a time), store them in a variable (as I will have to add the totals after each select) and continue to select in a while loop until no more records are found and then return the variable totals to the calling function. SELECT [OrderUser].OrderUserId, ISNULL(SUM(total.FileSize), 0), ISNULL(SUM(total.CompressedFileSize), 0) FROM ( SELECT DISTINCT TOP(100) ProductSize.OrderUserId, ProductSize.FileInfoId, CAST(ProductSize.FileSize AS BIGINT) AS FileSize, CAST(ProductSize.CompressedFileSize AS BIGINT) AS CompressedFileSize FROM ProductSize WITH (NOLOCK) INNER JOIN [Version] ON ProductSize.VersionId = [Version].VersionId ) AS total RIGHT OUTER JOIN [OrderUser] WITH (NOLOCK) ON total.OrderUserId = [OrderUser].OrderUserId WHERE NOT ([OrderUser].isCustomer = 1 AND [OrderUser].isEndOrderUser = 0 OR [OrderUser].isLocation = 1) AND [OrderUser].OrderUserId = 1 GROUP BY [OrderUser].OrderUserId

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  • How to check if a child-object is populated

    - by TheQ
    How can i check if a child-object of a linq-object is populated or not? Example code below. My model have two methods, one joins data, and the other does not: public static Member GetMemberWithPhoto(Guid memberId) { using (DataContext db = new DataContext()) { DataLoadOptions dataLoadOptions = new DataLoadOptions(); dataLoadOptions.LoadWith<Member>(x => x.UserPhoto); db.LoadOptions = dataLoadOptions; var query = from x in db.Members where x.MemberId == memberId select x; return query.FirstOrDefault(); } } public static Member GetMember(Guid memberId) { using (DataContext db = new DataContext()) { var query = from x in db.Members where x.MemberId == memberId select x; return query.FirstOrDefault(); } } Then my control have the following code: Member member1 = Member.GetMemberWithPhoto(memberId); Member member2 = Member.GetMember(memberId); Debug.WriteLine(member1.UserPhoto.ToString()); Debug.WriteLine(member2.UserPhoto.ToString()); The last line will generate a "Cannot access a disposed object" exception. I know that i can get rid of that exception just by not disposing the datacontext, but then the last line will generate a new query to the database, and i don't want that. What i would like is something like: Debug.WriteLine((member1.UserPhoto.IsPopulated()) ? member1.UserPhoto.ToString() : "none"); Debug.WriteLine((member2.UserPhoto.IsPopulated()) ? member2.UserPhoto.ToString() : "none"); Is it possible?

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  • Oracle: Finding Columns with only null values

    - by Jorge Valois
    I have a table with a lot of columns and a type column. Some columns seem to be always empty for a specific type. I want to create a view for each type and only show the relevant columns for each type. Working under the assumption that if a column has ONLY null values for a specific type, then that columns should not be part of the view, how can you find that out with queries? Is there a SELECT [columnName] FROM [table] WHERE [columnValues] ARE ALL [null] I know I COMPLETELY made it all up above... I'm just trying to get the idea across. Thanks in advance!

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  • A SELECT statement for Mysql

    - by Hossein
    I have this table: id,bookmarkID,tagID I want to fetch the top N bookmarkIDs for a given list of tags. Does anyone know a very fast solution for this? the table is quite large(12 million records) I am using MySql

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  • MySQL "NULL" questions

    - by Camran
    I have a table with several columns. Sometimes some of these column fields may be empty (ie. I won't use them in some cases). My questions: Would it be smart to set them to NULL in phpmyadmin? What does the "NULL" property actually do? Would I gain anything at all by setting them to NULL? Is it possible to use a NULL field the same way even though it is set to null?

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  • Transaction within a Transaction in C#

    - by Rosco
    I'm importing a flat file of invoices into a database using C#. I'm using the TransactionScope to roll back the entire operation if a problem is encountered. It is a tricky input file, in that one row does not necessary equal one record. It also includes linked records. An invoice would have a header line, line items, and then a total line. Some of the invoices will need to be skipped, but I may not know it needs to be skipped until I reach the total line. One strategy is to store the header, line items, and total line in memory, and save everything once the total line is reached. I'm pursuing that now. However, I was wondering if it could be done a different way. Creating a "nested" transaction around the invoice, inserting the header row, and line items, then updating the invoice when the total line is reached. This "nested" transaction would roll back if it is determined the invoice needs to be skipped, but the overall transaction would continue. Is this possible, practical, and how would you set this up?

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  • Extract time part from TimeStamp column in ORACLE

    - by RRUZ
    Actually i' am using MyTimeStampField-TRUNC(MyTimeStampField) to extract the time part from an timestamp column in Oracle. SELECT CURRENT_TIMESTAMP-TRUNC(CURRENT_TIMESTAMP) FROM DUAL this return +00 13:12:07.100729 this work ok for me, to extract the time part from an timestamp field, but i' m wondering if exist a better way (may be using an built-in function of ORACLE) to do this? Thanks.

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  • Calculating percent of votes inside mysql statement.

    - by Beck
    UPDATE polls_options SET `votes`=`votes`+1, `percent`=ROUND((`votes`+1) / (SELECT voters FROM polls WHERE poll_id=? LIMIT 1) * 100,1) WHERE option_id=? AND poll_id=? Don't have table data yet, to test it properly. :) And by the way, in what type % integers should be stored in database? Thanks for the help!

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  • Joining 3 tables - doing joins how to

    - by Kieran
    This is my current query - its not getting the required result. I want it do display all of the "resources" even if they dont have a connection. SELECT * FROM (`user_permissions`) JOIN `user_groups` ON `user_groups`.`id` = `user_permissions`.`role` JOIN `user_resources` ON `user_resources`.`id` = `user_permissions`.`resource` WHERE `role` = '4' When I try left join or right join it still returns the same result. The result I get is: id | role | resource | name 5 | 4 | 2 | Changelog I want id | role | resource | name 5 | 4 | 2 | Changelog null | null | null | Resource2 null | null | null | Resource3 Is this possible?

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  • C# - Password Database

    - by user335932
    So I want to make a program that allows you to store and search for user names/passwords for online sites there signed up to. I know C# has some database options but I don't know much about it. I also heard that it can read/write excel files. Whats do you think is best for storing the data? ALSO do databases need to be stored online on a sever, or can they reside in the program files?

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  • Do I need to drop index on temp table?

    - by Phil
    Hi, Fairly simple question, but I don't see it anywhere else on SO: Do indexes (indices?) on a temporary table get automatically deleted with the temporary table? I'd imagine they do but I don't really know how to check to make sure. Thanks, Phil

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  • Error while converting function from oracle to mssql

    - by sss
    Hi, I am migrating a function from oracle to mssql 2008.This function raises Select statements included within a function cannot return data to a client as error.How can i solve this problem? Original PLSQL Code CREATE OR REPLACE function f_birim_cevrim_katsayi (p_ID_MAMUL in number, p_ID_BIRIMDEN in number, p_ID_BIRIME in number) return number is v_katsayi number; begin v_katsayi:=0; if p_ID_BIRIMDEN!=p_ID_BIRIME then for c in ( select * from CR_BIRIM_CEVRIM where ID_MAMUL = p_ID_MAMUL and ( (ID_BIRIM = p_ID_BIRIMDEN and ID_BIRIM2 = p_ID_BIRIME) OR ( ID_BIRIM2 = p_ID_BIRIMDEN and ID_BIRIM = p_ID_BIRIME) ) and VALID = 1) loop if c.ID_BIRIM=p_ID_BIRIMDEN then v_katsayi:=c.MT_ORAN; else v_katsayi:=1/c.MT_ORAN; end if; end loop; else v_katsayi:=1; end if; return round(v_katsayi,10); exception when others then return 0; end; TSQL CODE If Exists ( SELECT name FROM sysobjects WHERE name = 'f_birim_cevrim_katsayi' AND type = 'FN') DROP FUNCTION f_birim_cevrim_katsayi GO CREATE FUNCTION f_birim_cevrim_katsayi ( @p_ID_MAMUL FLOAT , @p_ID_BIRIMDEN FLOAT , @p_ID_BIRIME FLOAT ) RETURNS float AS BEGIN DECLARE @adv_error INT DECLARE @v_katsayi FLOAT SELECT @v_katsayi = 0 IF @p_ID_BIRIMDEN != @p_ID_BIRIME BEGIN DECLARE cursor_for_inline_select1 CURSOR LOCAL FOR SELECT * FROM CR_BIRIM_CEVRIM WHERE ID_MAMUL = @p_ID_MAMUL AND ((ID_BIRIM = @p_ID_BIRIMDEN AND ID_BIRIM2 = @p_ID_BIRIME) OR (ID_BIRIM2 = @p_ID_BIRIMDEN AND ID_BIRIM = @p_ID_BIRIME)) AND VALID = 1 OPEN cursor_for_inline_select1 FETCH NEXT FROM cursor_for_inline_select1 WHILE (@@FETCH_STATUS <> -1) BEGIN IF c.ID_BIRIM = @p_ID_BIRIMDEN BEGIN SELECT @v_katsayi = c.MT_ORAN END ELSE BEGIN SELECT @v_katsayi = 1/c.MT_ORAN END END CLOSE cursor_for_inline_select1 DEALLOCATE cursor_for_inline_select1 END ELSE BEGIN SELECT @v_katsayi = 1 END DEALLOCATE cursor_for_inline_select1 return ROUND(@v_katsayi, 10) GOTO ExitLabel1 Exception1: BEGIN DEALLOCATE cursor_for_inline_select1 return 0 END ExitLabel1: return ROUND(@v_katsayi, 10) END GO

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  • join codition in sqlserver

    - by Pallavi
    after applying join condition on two tables i want records which is maximum among records of left table my query SELECT a1.*, t.*, ( a1.trnratefrom - t.trnratefrom )AS minrate, ( a1.trnrateto - t.trnrateto ) AS maxrate FROM (SELECT a.srno, trndate, b.trnsrno, Upper(Rtrim(Ltrim(b.trnstate))) AS trnstate, Upper(Rtrim(Ltrim(b.trnarea))) AS trnarea, Upper(Rtrim(Ltrim(b.trnquality))) AS trnquality, Upper(Rtrim(Ltrim(b.trnlength))) AS trnlength, Upper(Rtrim(Ltrim(b.trnunit))) AS trnunit, b.trnratefrom, b.trnrateto, a.remark, entdate FROM mstprodrates a INNER JOIN trnprodrates b ON a.srno = b.srno)a1 INNER JOIN (SELECT c.srno, trndate, d.trnsrno, Upper(Rtrim(Ltrim(d.trnstate))) AS trnstate, Upper(Rtrim(Ltrim(d.trnarea))) AS trnarea, Upper(Rtrim(Ltrim(d.trnquality))) AS trnquality, Upper(Rtrim(Ltrim(d.trnlength))) AS trnlength, Upper(Rtrim(Ltrim(d.trnunit))) AS trnunit, d.trnratefrom, d.trnrateto, c.remark, entdate FROM mstprodrates c INNER JOIN trnprodrates d ON c.srno = d.srno) AS t ON a1.trnstate = t.trnstate AND a1.trnquality = t.trnquality AND a1.trnunit = t.trnunit AND a1.trnlength = t.trnlength AND a1.trnarea = t.trnarea AND a1.remark = t.remark WHERE t.srno = (SELECT MAX(srno) FROM a1 WHERE srno < a1.srno)

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  • INSERT 0..n records into table 'A' based on content of table 'B' in MySql 5

    - by Robert Gowland
    Using MySql 5, I have a task where I need to update one table based on the contents of another table. For example, I need to add 'A1' to table 'A' if table 'B' contains 'B1'. I need to add 'A2a' and 'A2b' to table 'A' if table 'B' contains 'B2', etc.. In our case, the value in table 'B' we're interested is an enum. Right now I have a stored procedure containing a series of statements like: INSERT INTO A SELECT 'A1' FROM B WHERE B.Value = 'B1'; --Repeat for 'B2' -> 'A2a'; 'B2' -> 'A2b'; 'B3' -> 'A3', etc... Is there a nicer more DRY way of accomplishing this? Edit: There may be values in table 'B' that have no equivalent value for table 'A'.

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  • Help converting subquery to query with joins

    - by Tim
    I'm stuck on a query with a join. The client's site is running mysql4, so a subquery isn't an option. My attempts to rewrite using a join aren't going too well. I need to select all of the contractors listed in the contractors table who are not in the contractors2label table with a given label ID & county ID. Yet, they might be listed in contractors2label with other label and county IDs. Table: contractors cID (primary, autonumber) company (varchar) ...etc... Table: contractors2label cID labelID countyID psID This query with a subquery works: SELECT company, contractors.cID FROM contractors WHERE contractors.complete = 1 AND contractors.archived = 0 AND contractors.cID NOT IN ( SELECT contractors2label.cID FROM contractors2label WHERE labelID <> 1 AND countyID <> 1 ) I thought this query with a join would be the equivalent, but it returns no results. A manual scan of the data shows I should get 34 rows, which is what the subquery above returns. SELECT company, contractors.cID FROM contractors LEFT OUTER JOIN contractors2label ON contractors.cID = contractors2label.cID WHERE contractors.complete = 1 AND contractors.archived = 0 AND contractors2label.labelID <> 1 AND contractors2label.countyID <> 1 AND contractors2label.cID IS NULL

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