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• Is count(*) really expensive ?

  - by Anil Namde

  I have a page where I have 4 tabs displaying 4 different reports based off different tables. I obtain the row count of each table using a select count(*) from <table> query and display number of rows available in each table on the tabs. As a result, each page postback causes 5 count(*) queries to be executed (4 to get counts and 1 for pagination) and 1 query for getting the report content. Now my question is: are count(*) queries really expensive -- should I keep the row counts (at least those that are displayed on the tab) in the view state of page instead of querying multiple times? How expensive are COUNT(*) queries ?

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• Find maximum number of logged on users in SQL

  - by lleto

  Hi, I want to keep tabs on the number of concurrent users of my application. I therefore log a time_start and a time_stop. If I now want to query the database for the maximum number of logged on users and return the start date, how would I do that. The table looks like this: id | time_start | time_stop ----+---------------------+--------------------- 1 | 2010-03-07 05:40:59 | 2010-03-07 05:41:33 2 | 2010-03-07 06:50:51 | 2010-03-07 10:50:51 3 | 2010-02-21 05:20:00 | 2010-03-07 12:23:44 4 | 2010-02-19 08:21:12 | 2010-03-07 12:37:28 5 | 2010-02-13 05:52:13 | Where time_stop is empty the user is still logged on. In this case I would expect to see 2010-03-07 returned, since all users (5) were logged on at that moment. However if I would run the query with 'where time_start BETWEEN '2010-02-17' AND '2010-02-23' I would expect to see 2010-02-21 with a maximum of 2. Is this possible direct in SQL (using postgres) or do I need to parse the results in PHP? Thanks, lleto

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• Understanding the concept of Inodes

  - by darkie15

  Hi All, I am referring to the link: http://www.tux4u.nl/freedocs/unix/draw/inode.pdf I am confused on parts: 1 12 direct block pointers 2 1 single indirect block pointer 3 1 double indirect block pointer 4 1 triple indirect block pointer Now the diagram says that each pointer is 32/64 bits. [Query]: Why and how are these values inferred? I mean why specifically have only 32 or 64 bit pointers? The diagram says, One data block{8 KB} for each pointer {4 bytes/8 bytes} [Query]: How does this actually work out? i.e. 8*1024 bytes / 8 bytes = 1024 bytes? What is the logic behind having a 8 bytes pointer for 8KB block? Regards, darkie.

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• sql server 2008, not enough disc space

  - by snorlaks

  Hello, Im executing sql query on my database. I have sql server 2008 installed on my D harddrive which has 55 GB free space. I have also C drive which has sth like 150 MB free (right now). While executing that query on quite a big table (16 GB) I have an error: An error occurred while executing batch. Error message is: Not enough disc space. I would like to know if there is any possibility that I can make Sql server to use D drive instead of C Or maybe there is any other problem with what Im doing ? Thanks for help

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• jquery update div as text input is modified

  - by Piero

  Hi, So I have this text input in a form, and I want to update a div as the user types text in the text input. <p><label for="movie_name">Film: </label> <input type="text" name="movie_name" class="required" onkeydown="changediv2(this.value)" /></p> <p><div id="ajax_update"></div></p> My js method: function changediv2(str) { $('#ajax_update').html(geturl('http://url/search/movie?query='+str)); } If I type in a browser http://url/search/movie?query=someString, I get some html displayed. But when I call it via this ajax call, nothing happens... My geturl method: function geturl(addr) { var r = $.ajax({ type: 'GET', url: addr, async: false }).responseText; return r; } I cannot see what is wrong in there... Please help me! :)

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• Update music file details - Java.

  - by Desorder

  Hi all, Well, I'm a music fan guy, and now with my 18000 music collection, it's getting very hard to maintain. So, I would like to ask I could of question to help to write an app to maintain it for me. 1- How can I access a music file and read details of it? I mean, I would like to write some code and passing the directory, my app would read all the music files (understand mp3 files) and with that I would like to access details like title, artist, length and so on... 2- Is there a public source that I could access and update my file? A webservice somewhere that I could connect, query some information based on song name, or artist or whatever. I would like to achieve a final result of given a directory, my app would read the file, collect some information and query the source for a complete list of detail and update my file. Thank you guys for any help...

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• Ordering by multiple columns in mysql with subquery

  - by Scarface

  Hey guys I have a query that selects data and organizes but not in the correct order. What I want to do is select all the comments for a user in that week and sort it by each topic, then sort the cluster by the latest timestamp of each comment in their respective cluster. My current query selects the right data, but in seemingly random order. Does anyone have any ideas? select * from ( SELECT topic.topic_title, topic.topic_id FROM comments JOIN topic ON topic.topic_id=comments.topic_id WHERE comments.user='$user' AND comments.timestamp>$week order by comments.timestamp desc) derived_table group by topic_id

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• Mysql Master Slave Replication on Large Database table (how to sync initial data)

  - by Brian Lovett

  We have a production server and a dev server. We have found that backups are nearly impossible on the production server because of the query volume we experience. So, we're looking at setting up replication with our dev server being the slave. This is ideal because we can afford to lock the tables on that server and additionally it will be nice to have up to date data for the developers. Now, the issues. The production server can't really be taken down or locked at this point, at least not easily. We have a high query volume and fairly large 30+ GB innodb tables. Both servers are running all innodb and are also both on mysql 5.1. What can we do to sync the data initially to get replication started? I've tried a few options, but so far, none have worked.

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• Prevent duplicate rows with all non-unique columns (only with MySQL)?

  - by letseatfood

  Ho do I prevent a duplicate row from being created in a table with two columns, neither of which are unique? And can this be done using MySQL only, or does it require checks with my PHP script? Here is the CREATE query for the table in question (two other tables exist, users and roles): CREATE TABLE users_roles ( user_id INT(100) NOT NULL, role_id INT(100) NOT NULL, FOREIGN KEY (user_id) REFERENCES users(user_id), FOREIGN KEY (role_id) REFERENCES roles(role_id) ) ENGINE = INNODB; I would like the following query, if executed more than once, to throw an error: INSERT INTO users_roles (user_id, role_id) VALUES (1, 2); Please do not recommend bitmasks as an answer. Thanks!

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• MySQL Import Database Error because of Extended Inserts

  - by Castgame

  Hello all, I'm importing a 400MB(uncompressed) MySQL database. I'm using BIGDUMP, and I am getting this error: Stopped at the line 387. At this place the current query includes more than 300 dump lines. That can happen if your dump file was created by some tool which doesn't place a semicolon followed by a linebreak at the end of each query, or if your dump contains extended inserts. Please read the BigDump FAQs for more infos. I believe the file does contain Extended Inserts, however I have no way to regenerate the database as it has been deleted from the old server. How can I import this database or convert it to be imported? Thanks for any help. Best Nick EDIT: It appears the only viable answer is to separate the extended inserts, but I still need help figuring out how to split the file as the answer below suggests. Please help. Thank you.

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• Sort collection within collection using Linq

  - by user327066

  Hi, I have a one-to-many Linq query and I would like to sort on a property within the "many" collection. For example in the pseudo-code below, I am returned a List from the Linq query but I would like to sort / order the Products property based on the SequenceNumber property of the Product class. How can I do this? Any information is appreciated. Thanks. class Order { int OrderId; List<Product> Products; } class Product { string name; int SequenceNumber; }

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• Combobox select item in dropdown list C#

  - by Willem T

  I have an combobox poppulated with items from a database table. When I change the text i repopulate the combobox with items from the database table. But when I enter text and the list with suggestions opens no item in de list is selected. And i want a item to be selected so when you press enter that it becomes the selected item. This is a winforms application. Thanks. cbxNaam.Items.Clear(); string query = "SELECT bedr_naam FROM tblbedrijf WHERE bedr_naam LIKE '%" + cbxNaam.Text + "%'"; string[] bedrijfsnamen = Functions.DataTableToArray(Global.db.Select(query)); cbxNaam.Items.AddRange(bedrijfsnamen); cbxNaam.Select(cbxNaam.Text.Length + 1, 0);

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• Reduce the number of queries in EF

  - by Gio2k

  I have the following Model: Entities: Product (Contains basic data for products: price, etc) Attribute (Contains data for all possible optional attributes) ProductAttribute (Contains data for optional attributes of a product, eg. Color, Model, Size). ProductAttribute is essentially a many to many relationship with payload (ProductId, AttributeID, Value) And this piece of code: private static void ListAttributes(Product p) { p.ProductAttributes.Load(); foreach (var att in p.ProductAttributes) { att.Attribute.load(); Console.WriteLine("\tAttribute Name:{0} - Value {1}", att.Attribute.Name, att.AttributeValue); } } This piece of code will fire a query for each time the att.Attribute.Load() method is called in the foreach loop, only so i can get display the name of the attribute. I would like to fetch the Attribute.Name together with the query that fetches all attribute values, i.e. join ProductAttribute and Attribute. Is there any way to achieve this within my method?

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• MYSQL: How to limit inner join?

  - by Sergii Rechmp

  I need some help with my query. I have 2 tables: all: art|serie sootv: name|art|foo I need to get result like name|serie. My query is: SELECT t2.NAME, t1.serie FROM ( SELECT * FROM `all` WHERE `serie` LIKE '$serie' ) t1 INNER JOIN sootv t2 ON t1.art = t2.art; it works, but sootv table contains data like name|art|foo abc | 1 | 5 abc | 1 | 6 i get 2 same results. Its not what i need. Help me please - how i can get only one result: abc|1 Thanks.

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• Disk fragmentation when dealing with many small files

  - by Zorlack

  On a daily basis we generate about 3.4 Million small jpeg files. We also delete about 3.4 Million 90 day old images. To date, we've dealt with this content by storing the images in a hierarchical manner. The heriarchy is something like this: /Year/Month/Day/Source/ This heirarchy allows us to effectively delete days worth of content across all sources. The files are stored on a Windows 2003 server connected to a 14 disk SATA RAID6. We've started having significant performance issues when writing-to and reading-from the disks. This may be due to the performance of the hardware, but I suspect that disk fragmentation may be a culprit at well. Some people have recommended storing the data in a database, but I've been hesitant to do this. An other thought was to use some sort of container file, like a VHD or something. Does anyone have any advice for mitigating this kind of fragmentation? Additional Info: The average file size is 8-14KB Format information from fsutil: NTFS Volume Serial Number : 0x2ae2ea00e2e9d05d Version : 3.1 Number Sectors : 0x00000001e847ffff Total Clusters : 0x000000003d08ffff Free Clusters : 0x000000001c1a4df0 Total Reserved : 0x0000000000000000 Bytes Per Sector : 512 Bytes Per Cluster : 4096 Bytes Per FileRecord Segment : 1024 Clusters Per FileRecord Segment : 0 Mft Valid Data Length : 0x000000208f020000 Mft Start Lcn : 0x00000000000c0000 Mft2 Start Lcn : 0x000000001e847fff Mft Zone Start : 0x0000000002163b20 Mft Zone End : 0x0000000007ad2000

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• offset not working , want to do paging

  - by Rahul Mehta

  Hi, i have tried offset in simpledb but its not working as it working in mysql , and i want to do paging for my database api in php so that i send the pagenumber and pagelength to the query and it will return the data of that page only. How this i can do in simpledb. select * from second where time_stamp is not null and gibid = '54' and gibview = 'O' order by time_stamp asc limit $pagelength as offset is not working so i can't add offset in query. I have google and find there is next token is returned but i am not getting nexttoken. how to check for nexttoken. Please help . Thanks

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• Stored proc executes >30 secs when called from website, but <1 sec when called from ssms

  - by Blootac

  I have a stored procedure that is called by a website to display data. Today the web page has started timing out so I got profiler going and saw the query that was taking too long. I then ran the same query in management studio, under the same user login, and it takes less than a second to return. Is there anything obvious that could be causing this? I can't think of a reason why when ASP calls the stored proc it takes 30 secs but when I call it it's fine. Thanks

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• Paging and edit category status

  - by jasmine

  For edit home status of category I have a link: <span class=\"ha\" title=\"Active in Homepage\">Active in Homepage</span><a href=\"?page=homestatus&id={$row['id']}\" class=\"hp\" title=\"\">Passive in home page</a> and function: function homestatus() { $ID = mysql_real_escape_string($_GET['id']); $query = "UPDATE category SET home = 0 WHERE id= $ID "; $result = mysql_query($query); if (mysql_affected_rows () == 1) { header('Location: index.php?page=categories'); } } Everything works fine but there is paging : /index.php?page=categories&pg=2 I want that an item located in pg=2, redirected to index.php?page=categories&pg=2 How can I do this? Thanks in advance

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• Excluding a specific substring from a regex

  - by Matt S

  I'm attempting to mangle a SQL query via regex. My goal is essentially grab what is between FROM and ORDER BY, if ORDER BY exists. So, for example for the query: SELECT * FROM TableA WHERE ColumnA=42 ORDER BY ColumnB it should capture TableA WHERE ColumnA=42, and it should also capture if the ORDER BY expression isn't there. The closest I've been able to come is SELECT (.*) FROM (.*)(?=(ORDER BY)) which fails without the ORDER BY. Hopefully I'm missing something obvious. I've been hammering in Expresso for the past hour trying to get this.

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• jquery ajax form function(data)

  - by RussP

  Can some one please tell me where I have gone wrong. What ever I do I get the answer "no" JQuery to send data to php query $j.post("logincheck.php",{ username:$j('#username').attr('value'), password:$j('#password').attr('value'), rand:Math.random() } , function(data) { if(data=='yes') {alert('yes');} else {alert('no');} } ); Here is the php query if(isset($_POST['username'])): $username = $_POST['username']; $password = $_POST['password']; $posts = mysql_query("SELECT * FROM users WHERE username='$username'"); $no_rows = mysql_num_rows($posts ); while($row = mysql_fetch_array($posts)): print 'yes'; endwhile; else: print 'no'; //header('location: index.php'); endif; endif; Thank in adance

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• How to Deal with SET ANSI_NULLS ON or OFF ?

  - by Shantanu Gupta

  I want to call this procedure that sends one value that can be NULL or any int value. SELECT DomainName, DomainCode FROM Tags.tblDomain WHERE SubDomainId =@SubDomainId I simply want to use this single query rather than what i m doing right now in below given code. I searched for this how could i do this then i got this Link. According to this I have to set ANSI_NULLS OFF I am not able to set this inside this procedure before executing my sql query and then reset it again after doing this. ALTER PROCEDURE [Tags].[spOnlineTest_SubDomainSelect] @SubDomainId INT AS BEGIN -- SET NOCOUNT ON added to prevent extra result sets from -- interfering with SELECT statements. SET NOCOUNT ON; -- Insert statements for procedure here IF @SubDomainId IS NULL SELECT DomainName, DomainCode FROM Tags.tblDomain WHERE SubDomainId IS NULL ELSE SELECT DomainName, DomainCode FROM Tags.tblDomain WHERE SubDomainId =@SubDomainId END What will be the better practice to do deal with ANSI_NULLS or Using If Else

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• How to create following cube?

  - by Itsgkiran

  Hi! For example........... Database Table: BatchID BatchName Chemical Value -------------------------------------------------------- BI-1 BN-1 CH-1 1 BI-2 BN-2 CH-2 2 -------------------------------------------------------- I need to display following cube BI-1 BI-2 BN-1 BN-2 ----------------------------------------- CH-1 1 null ------------------------------------------ CH-2 null 2 ------------------------------------------ Here BI-1,BN-1 are two rows in a single columns i need to display chemical value as row of that. What is query MDX query for this. Could Please help me to solve this problem. Thank You.

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• What's the difference between /123 and /?123?

  - by BoltClock

  I've noticed that some sites (including http://jobs.stackoverflow.com) have query strings that look like this: http://somewebapp.example/?123 as compared to: http://somewebapp.example/123 or http://somewebapp.example/id/123 What are the reasons that developers choose to implement their web apps' URLs using the first example instead of the second and third examples? And as a bonus, how would one implement the first example in PHP, given that 123 is the primary key of some row in a database table? (I just need to know how to retrieve 123 from the URL; I already know how to query the database for a primary key of 123.)

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• Reusing an anonymous parameter in a prepared statement

  - by Chris Lieb

  I am customizing the insert SQL generated by hibernate and have hit an issue. When Hibernate generates the query by itself, it inserts data into the first two columns of the table, but this causes a database error since all four columns of the table are non-nullable. For the insert to be performed properly, it must insert the same data into two columns of the new record. This means that I need Hibernate to bind the same data to two different parameters in the query (prepared statement) that I am writing. Is there some SQL syntax that allows me to refer to anonymous parameters bound to a prepared statement in an order different from which they are bound? Details REF_USER_PAGE_XREF ---------------------------------------- PK FK1 | NETWORK_ID | VARCHAR2(100) PK FK1 | PAGE_PATH | VARCHAR2(1000) | USER_LAST_UPDT | VARCHAR2(100) | TMSP_LAST_UPDT | DATE insert into REF_USER_ROLE_XREF( NETWORK_ID, PAGE_PATH, TMSP_LAST_UPDT, USER_LAST_UPDT) values ( ?, /* want to insert the same data here */ ?, ?, /* and here */ (select to_char(sysdate, 'DD-MON-YY') from dual) I want to insert the same data into the first and third anonymous parameters.

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• Fill in missing values in a SELECT statement

  - by benjamin button

  If i have a table with two fields.customer id and order. let's say i have in total order ID 1,2,3,4 all the customer can have all the four orders.like below 1234 1 1234 2 1234 3 1234 4 3245 3 3245 4 5436 2 5436 4 you can see above that 3245 customer doesnt have order id 1 and 2. how could i print in the query output like 3245 1 3245 2 5436 1 5436 3 EDIT: i dont have order table but i have list of order's like we can hard code it in the query(1,2,3,4) i dont have an orders table.

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