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  • How do I select a random record efficiently in MySQL?

    - by user198729
    mysql> EXPLAIN SELECT * FROM urls ORDER BY RAND() LIMIT 1; +----+-------------+-------+------+---------------+------+---------+------+-------+---------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+---------------+------+---------+------+-------+---------------------------------+ | 1 | SIMPLE | urls | ALL | NULL | NULL | NULL | NULL | 62228 | Using temporary; Using filesort | +----+-------------+-------+------+---------------+------+---------+------+-------+---------------------------------+ The above doesn't qualify as efficient,how should I do it properly?

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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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  • Clustered index on frequently changing reference table of one or more foreign keys

    - by Ian
    My specific concern is related to the performance of a clustered index on a reference table that has many rapid inserts and deletes. Table 1 "Collection" collection_pk int (among other fields) Table 2 "Item" item_pk int (among other fields) Reference Table "Collection_Items" collection_pk int, item_pk int (combined primary key) Because the primary key is composed of both pks, a clustered index is created and the data physically ordered in the table according to the combined keys. I have many users creating and deleting collections and adding and removing items to those collections very frequently affecting the "Collection_Items" table, and its clustered index. QUESTION PART: Since the "Collection_Items" table is so dynamic, wouldn't there be a big performance hit on constantly resorting the table rows because of the clustered index ? If yes, what should I do to minimize this ?

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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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  • How to join two query in SQL (Oracle)

    - by MAHESH A SONI
    How can I join these queries? SELECT RCTDT, SUM(RCTAMOUNT), COUNT(RCTAMOUNT) FROM RECEIPTS4 WHERE RCTDT BETWEEN '01-nov-2009' AND '30-nov-2009' AND RCTTYPE='CA' AND RCTAMOUNT>0 GROUP BY RCTDT --- SELECT RCTDT, SUM(RCTAMOUNT), COUNT(RCTAMOUNT) FROM RECEIPTS4 WHERE RCTDT BETWEEN '01-nov-2009' AND '30-nov-2009' AND RCTTYPE='CQ' AND RCTAMOUNT>0 GROUP BY RCTDT

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  • Query crashes MS Access

    - by user284651
    THE TASK: I am in the process of migrating a DB from MS Access to Maximizer. In order to do this I must take 64 tables in MS ACCESS and merge them into one. The output must be in the form of a TAB or CSV file. Which will then be imported into Maximizer. THE PROBLEM: Access is unable to perform a query that is so complex it seems, as it crashes any time I run the query. ALTERNATIVES: I have thought about a few alternatives, and would like to do the least time-consuming one, out of these, while also taking advantage of any opportunities to learn something new. Export each table into CSVs and import into SQLight and then make a query with it to do the same as what ACCESS fails to do (merge 64 tables). Export each table into CSVs and write a script to access each one and merge the CSVs into a single CSV. Somehow connect to the MS ACCESS DB (API), and write a script to pull data from each table and merge them into a CSV file. QUESTION: What do you recommend?

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  • Running an application from an USB device...

    - by Workshop Alex
    I'm working on a proof-of-concept application, containing a WCF service with console host and client, both on a single USB device. On the same device I will also have the client application which will connect to this service. The service uses the entity framework to connect to the database, which in this POC will just return a list of names. If it works, it will be used for a larger project. Creating the client and service was easy and this works well from USB. But getting the service to connect to the database isn't. I've found this site, suggesting that I should modify machine.config but that stops the XCopy deployment. This project cannot change any setting of the PC, so this suggestion is bad. I cannot create a deployment setup either. The whole thing just needs to run from USB disk. So, how do I get it to run? (The service just selects a list of names from the database, which it returns to the client. If this POC works, it will do far more complex things!)

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  • Manual Linq to SQL entity framework mapping

    - by kprobst
    I've been playing with the O/R designer in VS and I was wondering if someone could shed come light on this. I'm used to OR mappers that are largely manual (homegrown and e.g., NHibernate). I don't mind encoding the entity classes myself, since they don't change all that often to begin with, and I have this irrational fear of designers and auto generated code as it is. I have noticed that the generated entity classes contain a lot of boilerplate extensibility methods, e.g. On[Property]Changed() and so on where [Property] is a mapped member of the class. These are placed in the setters of the property accessors. I assume it's OK if I don't include these when I do my hand coding, correct? They would be nice if I needed some sort of interception pattern but that's certainly not the case. I guess I just need to know if any of those methods are required by the entity framework to keep track of changes to the mapping types in order for things to work when updating the database. Thanks!

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  • Subsonic SELECT FROM msdb

    - by Lukasz Lysik
    Hi, I want to execute the following query using Subsonic: SELECT MAX([restore_date]) FROM [msdb].[dbo].[restorehistory] While the aggregate part is easy for me, the problem is with the name of the table. How should I force Subsonic to select from different database than default one.

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  • Inexplicably slow query in MySQL

    - by Brandon M.
    Given this result-set: mysql> EXPLAIN SELECT c.cust_name, SUM(l.line_subtotal) FROM customer c -> JOIN slip s ON s.cust_id = c.cust_id -> JOIN line l ON l.slip_id = s.slip_id -> JOIN vendor v ON v.vend_id = l.vend_id WHERE v.vend_name = 'blahblah' -> GROUP BY c.cust_name -> HAVING SUM(l.line_subtotal) > 49999 -> ORDER BY c.cust_name; +----+-------------+-------+--------+---------------------------------+---------------+---------+----------------------+------+----------------------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+--------+---------------------------------+---------------+---------+----------------------+------+----------------------------------------------+ | 1 | SIMPLE | v | ref | PRIMARY,idx_vend_name | idx_vend_name | 12 | const | 1 | Using where; Using temporary; Using filesort | | 1 | SIMPLE | l | ref | idx_vend_id | idx_vend_id | 4 | csv_import.v.vend_id | 446 | | | 1 | SIMPLE | s | eq_ref | PRIMARY,idx_cust_id,idx_slip_id | PRIMARY | 4 | csv_import.l.slip_id | 1 | | | 1 | SIMPLE | c | eq_ref | PRIMARY,cIndex | PRIMARY | 4 | csv_import.s.cust_id | 1 | | +----+-------------+-------+--------+---------------------------------+---------------+---------+----------------------+------+----------------------------------------------+ 4 rows in set (0.04 sec) I'm a bit baffled as to why the query referenced by this EXPLAIN statement is still taking about a minute to execute. Isn't it true that this query only has to search through 449 rows? Anyone have any idea as to what could be slowing it down so much?

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  • LINQ - if condition

    - by ile
    In code, the commented part is what I need to solve... Is there a way to write such query in LINQ? I need this because I will need sorting based on Status. var result = ( from contact in db.Contacts join user in db.Users on contact.CreatedByUserID equals user.UserID join deal in db.Deals on contact.ContactID equals deal.ContactID into deals orderby contact.ContactID descending select new ContactListView { ContactID = contact.ContactID, FirstName = contact.FirstName, LastName = contact.LastName, Email = contact.Email, Deals = deals.Count(), EstValue = deals.Sum(e => e.EstValue), SalesAgent = user.FirstName + " " + user.LastName, Tasks = 7, // This is critical part if(Deals == 0) Status = "Prospect"; else Status = "Client"; // End of critical part... }) .OrderBy(filterQuery.OrderBy + " " + filterQuery.OrderType) .Where(filterQuery.Status);

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  • multi-row update table with "different" data

    - by kralco626
    I think the best way to explain this is to tell you what I have. I have two tables A and B both have columns Field1 and Field2. However Field 2 is not populated in table B I want to populate field 2 of table B with field 2 of table A where field 1 of table A matches field 1 of table B. something like update tableB set Field2 = tableA.field2 where tablea.field1 = tableb.field1. The reason this may seem so odd and obscure is that I'm tyring to do an inital data load form an old database to a new one. please let me know if you need clarification

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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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  • Getting the last element of a Postgres array, declaratively

    - by Wojciech Kaczmarek
    How to obtain the last element of the array in Postgres? I need to do it declaratively as I want to use it as a ORDER BY criteria. I wouldn't want to create a special PGSQL function for it, the less changes to the database the better in this case. In fact, what I want to do is to sort by the last word of a specific column containing multiple words. Changing the model is not an option here. In other words, I want to push Ruby's sort_by {|x| x.split[-1]} into the database level. I can split a value into array of words with Postgres string_to_array or regexp_split_to_array functions, then how to get its last element?

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  • allowing bb code but not java script

    - by user1405062
    Hello im trying to get the hang of using bb codes onto my normal php site ( not forum or anything just a normal site ) I have seen a few posts like this one http://www.pixel2life.com/forums/index.php?/topic/10659-php-bbcode-parser/ which says i need a bb parser. I was just wondering can anyone show me how i would use one ? I have a status box were users can update there status but i would like to allow bb codes but not java script. So when im doing my inserting into the db i strip the status like so.. $status= mysql_real_escape_string($_POST['status']); $status2= strip_tags($status); And that stops the java script and tags from getting though but i need the bb code tags to come though but carry on blocking the java script code is there anyway to do this ? Also then i just echo it out echo $status2 ; But just plain text shows so was just wondering if anyone knows how to let though bb code and stop java script and could some one show me how to use the bb parasher ? also need to know how to echo out the bb coding...

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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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  • Getting "too many rows" error inside a "for" cursor loop

    - by Will
    I have a trigger that contains two cursors loops, one nested inside the other like this: FOR outer_rec IN outer_cursor LOOP FOR inner_rec IN inner_cursor LOOP -- Do some calculations END LOOP; END LOOP; Somewhere in this it is throwing the following error: ORA-01422: exact fetch returns more than requested number of rows I've been trying to determine where it's coming from for an hour or so.. but should this error never happen? Also.. I am assuming the inner loop automatically closes and opens itself again every time the outer loop goes the next record, i hope this is correct.

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  • .tpl files and website problem

    - by whitstone86
    Apologies if the title is in lowercase but it's describing an extension format. I've started using Dwoo as my template engine for PHP, and am not sure how to convert my PHP files into .tpl templates. My site is similar to, but not the same as, http://library.digiguide.com/lib/programme/Medium-319648/Drama/ with its design (except colour scheme and site name are different, plus it's in PHP - so copyright issues are avoided here, the design arguably could be seen as parody even though the content is different. The database is called tvguide, and it has these tables: Programmes House M.D. Medium Police Stop! American Dad! The tablenames of the above programmes are: housemdonair mediumonair policestopair americandad1 Episodes The tablenames for the above programmes' episode guides are: housemdepidata mediumepidata policestopepidata americandad1epidata All of them have the following rows: id (not an auto-increment, since I wish to dynamically generate a page from this) episodename seriesnumber episodenumber episodesynopsis (the above four after id do exactly as stated) I have a pagination script that works, it displays 20 records per page as I want it to. This is called pmcPagination.php - but I won't post it in full since it would take up too much space. However, I'm trying to get it so that variables are filled in like this: (ok, so the examples below are ASP.NET, but if there's a PHP/MySQL equivalent I would gratefully appreciate this!!): http://library.digiguide.com/lib/episode/741168 http://library.digiguide.com/lib/episode/714829 with the episode detail and data. My site works, but it's fairly basic, and it's not online yet until my bugs are fixed. Mod_rewrite is enabled so my site reads as http://mytvguide.com/episode/123456 or http://mytvguide.com/programme/123456 http://mytvguide.com/WorldInAction/123456/Documentary/ I've tried looking on Google, but am not sure how to get this TV guide script to work at its best - but I think .tpl, and .php/MySQL is the way to go. Any advice anyone has on making this project into a fully workable, ready to use site would be much appreciated, I've spent months refining this project! P.S. Apologies for the length of this, hope it describes my project well.

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