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• how to handle db concurrency in client-server application in C#?

  - by RAJ K

  I am developing an application in C# WPF which will have Client-Server architecture (Client will do products sales billing). I am novice in this area and I asked this question to start my development process. Click here to view question. So, ultimately I have selected MySQl, WCf & WPF. Now I have one silly question. Do i need to handle DB concurrency explicitly in my application (like 3 clients inserting data same time) or MySQl will handle this without any conflict? To accomplish my project i thought, I will create a service in WCf which will do DB queries from client application. Do you have any suggestion to improve my application performance.

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• Store database, good pattern for simultaneous access

  - by dygi

  I am kinda new to database designing so i ask for some advices or some kind of a good pattern. The situation is that, there is one database, few tables and many users. How should i design the database, or / and which types of queries should i use, to make it work, if users can interact with the database simultaneously? I mean, they have access to and can change the same set of data. I was thinking about transactions, but I am not sure, if that is the right / good / the only solution. I will appreciate some google keywords too.

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• MySQL Query still executing after a day..?

  - by Matt Jarvis

  Hi - I'm trying to isolate duplicates in a 500MB database and have tried two ways to do it. One creating a new table and grouping: CREATE TABLE test_table as SELECT * FROM items WHERE 1 GROUP BY title; But it's been running for an hour and in MySQL Admin it says the status is Locked. The other way I tried was to delete duplicates with this: DELETE bad_rows.* from items as bad_rows inner join ( select post_title, MIN(id) as min_id from items group by title having count(*) 1 ) as good_rows on good_rows.post_title = bad_rows.post_title; ..and this has been running for 24hours now, Admin telling me it's Sending data... Do you think either or these queries are actually still running? How can I find out if it's hung? (with Apple OS X 10.5.7)

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• Is there an open source repository for SQL code?

  - by morpheous

  I find myself writing SQL code (queries or stored procs) to solve problems that can definitely be defined as 'patterns' that occur frequently in business. Rather than having to wrack my brain each time I encounter a new problem (which must have been solved a countless times by other coders/db analysts, I wondered if there was a repository I could go to check out (peer reviewed) code - and maybe add my two pence every now and then. I know different db vendors tend to write slightly variant forms of SQL - but there could still be a repository with ANSI stuff and proprietary stuff. Hopefully, such a site would encourage more people to write standardized SQL. Is there such a site?. If no - why not? (would anyone else be interested in such a site?) If such a site exists, please provide link(s), as Google is not finding anything remotely useful.

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• TSQL - compare tables

  - by Rya

  I want to create a stored procedure that compares the results of two queries. If the results of the 2nd table can be found in the first, print 'YES', otherwise, print 'No'. Table 1: SELECT dbo.Roles.RoleName, dbo.UserRoles.RoleID FROM dbo.Roles LEFT OUTER JOIN dbo.UserRoles ON dbo.Roles.RoleID = dbo.UserRoles.RoleID WHERE (dbo.Roles.PortalID = 0) AND (dbo.UserRoles.UserID = 2) Table 2: Declare @RowData as nvarchar(2000) Set @RowData = ( SELECT EditPermissions FROM vw_XMP_DMS_Documents where DocumentID = 2) Select Data from dbo.split(@RowData, ',') For example. Table 1: John Jack James Table 2: John Sally Jane Print 'YES' Is this possible??? Thank you all very much. -R

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• How do you optimize database performance when providing results for autocomplete/iterative search?

  - by Howiecamp

  Note: In this question I'm using the term "autocomplete" (or "iterative search") to refer to returning search-as-you-type results, e.g. like Google Search gives you. Also my question is not specific to web applications vs. fat client apps. How are SQL SELECT queries normally constructed to provide decent performance for this type of query, especially over arbitrarily large data sets? In the case where the search will only query based on the first n characters (easiest case) am I still issuing a new SELECT result FROM sometable WHERE entry LIKE... on each keypress. Even with various forms of caching this seems like it might result in poor performance. In cases where you want your search string to return results with prefix matches, substring matches, etc. it's an even more difficult problem. Looking at a case of searching a list of contacts, you might return results that match FirstName + LastName, LastName + FirstName, or any other substring.

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• Do MySQL Locked Tables affect related Views?

  - by CogitoErgoSum

  So after reading http://stackoverflow.com/questions/1415602/performance-in-pdo-php-mysql-transaction-versus-direct-execution in regards to performance issues I was thinking about I did some research on locking tables in MySQL. On http://dev.mysql.com/doc/refman/5.0/en/table-locking.html Table locking enables many sessions to read from a table at the same time, but if a session wants to write to a table, it must first get exclusive access. During the update, all other sessions that want to access this particular table must wait until the update is done. This part struck me particularly becuase most of our queries will be updates rather than inserts. I was wondering if one created a table called foo on which all updates/inserts were carried out and then a view called foo_view (A copy of foo, or perhaps foo and a linkage of several other tables plus foo) on which all selects occured, would this locking issue still occur? That is, would SELECT quries on foo_view still have to wait for an update to finish on foo?

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• Solr match all aka *:* does not work

  - by Karussell

  Don't know what I did wrong. I have two indices with identical documents in it. The local index was replicated from a master which responds correctly, so the same solrconfig.xml and schema.xml file. But if I query the index on my local machine with *:* I get 0 docs. (other queries on my local machine are working correct) I tried jetty and tomcat for the local index. no success. The *:* behaviour is crucial for me, because some test cases are failing now. Do you have an idea what could be wrong?

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• In Java how instance of and type cast(i.e (ClassName)) works on proxy object ?

  - by learner

  Java generates a proxy class for a given interface and provides the instance of the proxy class. But when we type cast the proxy object to our specific Object, how java handles this internally? Is this treated as special scenario? For example I have class 'OriginalClass' and it implements 'OriginalInterface', when I create proxy object by passing 'OriginalInterface' interface java created proxy class 'ProxyClass' using methods in the provided interface and provides object of this class(i.e ProxyClass). If my understanding is correct then can you please answer following queries 1) When I type cast object of ProxyClass to my class OriginalClass this works, but how java is allowing this? Same in case of instace of? 2) As my knowledge java creates a proxy class only with the methods, but what happen when I try to access attributes on this object? 3) Only interface methods are getting implemented in Proxy, but what happens when I try to access a method which not in interface and only mentioned in the class? Thanks, Student

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• possibility to do type/data conversion of data returned by ria services?

  - by reinier

  My service returns an byte array, which I have to convert to an 'animated gif' (using imagetools since silverlight doesn't support it yet) I was wondering, is it possible to insert some code at the client, where I can do the conversion before the actual object is returned to whatever it is binded against? On the server side, the queries can be customized before it is sent over the wire. I'm asking for the exact opposite, can I do some on the fly conversions the moment they get of the wire and before they are returned to the controls. If I'm overthinking this and there is a smarter/better/easier way to do it, I'm all for such an answer as well

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• SQL Query to select upcoming events with a start and end date

  - by Chris T

  I need to display upcoming events from a database. The problem is when I use the query I'm currently using any events with a start day that has passed will show up lower on the list of upcoming events regardless of the fact that they are current My table (yaml): columns: title: type: string(255) notnull: true default: Untitled Event start_time: type: time end_time: type: time start_day: type: date notnull: true end_day: type: date description: type: string(500) default: This event has no description category_id: integer My query (doctrine): $results = Doctrine_Query::create() ->from("sfEventItem e, e.Category c") ->select("e.title, e.start_day, e.description, e.category_id, e.slug") ->addSelect("c.title, c.slug") ->orderBy("e.start_day, e.start_time, e.title") ->limit(5) ->execute(array(), Doctrine_Core::HYDRATE_ARRAY); Basically I'd like any events that is currently going on (so if today is in between start_day and end_day) to be at the top of the list. How would I go about doing this if it's even possible? Raw sql queries are good answers too because they're pretty easy to turn into DQL.

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• HOw do I limit array to a certain number??

  - by mathew

  I do have an array which queries database..what I need to do is control this array to a certain number say 10. but I dont want to set LIMIT in mysql query I need to leave that as it is... $result = mysql_query("SELECT * FROM query ORDER BY regtime DESC"); while($row = mysql_fetch_array($result)) { echo "<img src='bullet.gif' align='absmiddle' class='col1ab'><a class='col1ab' href=".$row['web']." >www.".$row['web']."</a><br>"; } How do I limit this array to certain limit??

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• Database Engine not appearing in SQL Server listing

  - by Jonn

  I don't know if I'm searching for the wrong queries in google but I can't seem to find an answer to this. I have SQL Server 2008 installed in my pc and according to services.msc, I've got 2 database engines running: SQLEXPRESS (probably one that came along with Visual Studio) and MSSQLSERVER. When I try to connect only SQLEXPRESS is visible in the Server Name drop down list. I tried to explicitly state MSSQLSERVER by typing in MYPCNAME\MSSQLSERVER Didn't work. The best solution I could find in the internet was to enable stuff at Configuration Manager. Didn't work either (although I did find that TCP/VIA and all other options were disabled for MSSQLSERVER). Anyone have any other ideas on what I should try next or probably something that I overlooked?

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• Deserializing only select properties of an Entity using JDOQL query string?

  - by user246114

  Hi, I have a rather large class stored in the datastore, for example a User class with lots of fields (I'm using java, omitting all decorations below example for clarity): @PersistenceCapable class User { private String username; private String city; private String state; private String country; private String favColor; } For some user queries, I only need the favColor property, but right now I'm doing this: SELECT FROM " + User.class.getName() + " WHERE username == 'bob' which should deserialize all of the entity properties. Is it possible to do something instead like: SELECT username, favColor FROM " + User.class.getName() + " WHERE username == 'bob' and then in this case, all of the returned User instances will only spend time deserializing the username and favColor properties, and not the city/state/country properties? If so, then I suppose all the other properties will be null (in the case of objects) or 0 for int/long/float? Thank you

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• Is file_get_contents multi line?

  - by Abs

  Hello all, Does file_get_contents maintain line breaks? I thought it did but I have tried this: if($conn){ $tsql = file_get_contents('scripts/CreateTables/SLR05_MATCH_CREATETABLES.sql'); $row = sqlsrv_query($conn, $tsql); print_r(sqlsrv_errors()); } The errors I get is that SQL Server complains that there is incorrect syntax. I get the same errors when I run the SQL Script without any line breaks, which suggests file_get_contents removes them? When I run the script normally (open the file in SQL Server Management Studio) and execute it, it works perfectly. So is there something that I can use that maintains line breaks etc? Or is there another problem here in using queries from a file with the SQL Server PHP Driver from Microsoft? Thanks all for any help

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• Does Oracle 11g automatically index fields frequently used for full table scans?

  - by gustafc

  I have an app using an Oracle 11g database. I have a fairly large table (~50k rows) which I query thus: SELECT omg, ponies FROM table WHERE x = 4 Field x was not indexed, I discovered. This query happens a lot, but the thing is that the performance wasn't too bad. Adding an index on x did make the queries approximately twice as fast, which is far less than I expected. On, say, MySQL, it would've made the query ten times faster, at the very least. I'm suspecting Oracle adds some kind of automatic index when it detects that I query a non-indexed field often. Am I correct? I can find nothing even implying this in the docs.

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• DB management for Heroku apps

  - by zetarun

  Hi all, I'm fairly new to both Rails and Heroku but I'm seriously thinking of using it as a platform to deploy my Ruby/Rails applications. I want to use all the power of Heroku, so I prefer the "embedded" PostgreSQL managed by Heroku instead of the addon for Amazon RDS for MySQL, but I'm not so confident without the possibility to access my data in a SQL client... I know that in a well made app you have no need to access DB, but there are some situations (add rows to a config table, see data not mapped in a view, update some columns for debugging issues, performance monitoring, running queries for reporting, etc.) when this can be good... How do you solve this problem? What's you experience in a real life app powered by Heroku? Thanks!

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• Index for wildcard match of end of string

  - by Anders Abel

  I have a table of phone numbers, storing the phone number as varchar(20). I have a requirement to implement searching of both entire numbers, but also on only the last part of the number, so a typical query will be: SELECT * FROM PhoneNumbers WHERE Number LIKE '%1234' How can I put an index on the Number column to make those searchs efficient? Is there a way to create an index that sorts the records on the reversed string? Another option might be to reverse the numbers before storing them, which will give queries like: SELECT * FROM PhoneNumbers WHERE ReverseNumber LIKE '4321%' However that will require all users of the database to always reverse the string. It might be solved by storing both the normal and reversed number and having the reversed number being updated by a trigger on insert/update. But that kind of solution is not very elegant. Any other suggestions?

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• advanced search with mysql

  - by Arsenal

  I'm creating a search function for my website where the user can put in anything he likes in a textfield. It get's matched against anything (name, title, job, car brand, ... you name it) I initially wrote the query with an INNER JOIN on every table that needed to be searched. SELECT column1, column2, ... FROM person INNER JOIN person_car ON ... INNER JOIN car ... This ended up in a query with 6 or 8 INNER JOINs, and a whole lot WHERE ... LIKE '%searchvalue%' Now this query seems to cause a time'out in MySql, and I even got a warning from my hosting provider that the queries just taking up too many resources. Now obviously I'm doing this very wrong, but I was wondering how the correct approach to these kind of search functions is. Thanks!

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• Django - User account with multiple identities

  - by Scott Willman

  Synopsis: Each User account has a UserProfile to hold extended info like phone numbers, addresses, etc. Then, a User account can have multiple Identities. There are multiple types of identities that hold different types of information. The structure would be like so: User |<-FK- UserProfile | |<-FK- IdentityType1 |<-FK- IdentityType1 |<-FK- IdentityType2 |<-FK- IdentityType3 (current) |<-FK- IdentityType3 |<-FK- IdentityType3 The User account can be connected to n number of Identities of different types but can only use one Identity at a time. Seemingly, the Django way would be to collect all of the connected identities (user.IdentityType1_set.select_related()) into a QuerySet and then check each one for some kind of 'current' field. Question: Can anyone think of a better way to select the 'current' marked Identity than doing three DB queries (one for each IdentityType)?

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• How can an SQL query return data from multiple tables

  - by Fluffeh

  I would like to know how to get data from multiple tables in my database, what types of methods are there to do this, what are joins and unions and how are they different from one another? When should I use each one compared to the others? I am planning to use this in my (for example - PHP) application, but don't want to run multiple queries against the database, what options do I have to get data from multiple tables in a single query? Note: I am writing this as I would like to be able to link to a well written guide on the numerous questions that I constantly come across in the PHP queue, so I can link to this for further detail when I post an answer. The answers cover off the following: Part 1 - Joins and Unions Part 2 - Subqueries Part 3 - Tricks and Efficient Code

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• Suggest Sphinx index scheme

  - by htf

  Hi. In a MySQL database I have documents of different type: some have text content, meta keys, descriptions, others have code, SKU number, size and brand name and so on. The problem is, I have to search something in all of these documents and then display a single page, where the results will be grouped by the document type, such as help page, blog post, item... It's not clear for me how to implement the Sphinx index: I want to have a single index to speed up queries, but since different docs have different structure - how can I group them? I was thinking about just concatenating them, but it just doesn't feel right.

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• Specify sorting order for a GROUP BY query to retrieve oldest or newest record for each group

  - by Beau Simensen

  I need to get the most recent record for each device from an upgrade request log table. A device is unique based on a combination of its hardware ID and its MAC address. I have been attempting to do this with GROUP BY but I am not convinced this is safe since it looks like it may be simply returning the "top record" (whatever SQLite or MySQL thinks that is). I had hoped that this "top record" could be hinted at by way of ORDER BY but that does not seem to be having any impact as both of the following queries returns the same records for each device, just in opposite order: SELECT extHwId, mac, created FROM upgradeRequest GROUP BY extHwId, mac ORDER BY created DESC SELECT extHwId, mac, created FROM upgradeRequest GROUP BY extHwId, mac ORDER BY created ASC Is there another way to accomplish this? I've seen several somewhat related posts that have all involved sub selects. If possible, I would like to do this without subselects as I would like to learn how to do this without that.

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• Slow server response time - CakePHP

  - by Hasan

  I am using CakePHP 1.2 for building a website. The problem i am facing is when ever a page loads it takes a lot of time in "waiting for www.example.com". The server response time is very slow. First i thot it was my database queries, but they were executing in less than seconds time. Next i also contacted the server people. They told it was not the server. Now i am stuck very badly with "waiting for www.example.com". Is the problem is in coding or the cakePHP is mis configured. Need help badly and fast. Thanks

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• why LINQ 2 SQL sometime add a field like select 1 as test, others valid fields....

  - by Fredou

  I have to concat 2 linq2sql query and I have an issue since the 2 query doesn't return the same number of columns, what is weird is after a .ToList() on the queries, they can concat without problem. The reason is, for some linq2sql reason, I have 2 more column named test and test2 which come from 2 left outer join that linq2sql automatically create, something like "select 1 as test, tablefields" Is there any good reason for that? how to remove this extra "1 as test" field? here a few of examples of what it look like: google result for linq 2 sql "select 1 as test"

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