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• SQL - query inside NOT IN takes longer than the complete query ??

  - by Aleksandar Tomic

  Hi every1, I'm using NOT IN inside my SQL query. For example: select columnA from table1 where columnA not in ( select columnB from table2) How is it possible that this part of the query select columnB from table2 takes 30sec to complete, but the whole query above takes 0.1sec to complete?? Shouldn't the complete query take 30sec + ? BTW, both queries return valid results. Thanks! Answers to Comments Is it because the second query hasn't actually completed but has only returned back the first 'x' rows (out of a very large table?) No, the query is completed after 30 seconds, not to many rows returned (eg. 50). But @Aleksandar wondered why the question congaing the performance killer was so fast. my point exactly Also how long does select distinct columnB from table2 take to execute? actually, the original query is "select distinct...

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• Relying on nhibernate's second level cache vs pushing objects into asp.net session

  - by AhmetC

  I have some big entities which are frequently accessed in the same session. For example, in my application there is a reporting page which consist of dynamically generated chart images. For each chart image on this page, the client makes requests to corresponding controller and the controller generates images using some entities. I can either use asp.net's session dictionary for "caching" those entities or rely on nhibernate's second level cache support with using cached queries for example. What is your opinion? By the way I will use shared hosting, is nhibernate's second level cache hosting friendly? Thanks.

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• What's the cause of (and treatment for) this java MySQL exception?

  - by justkevin

  I'm getting the following exception when executing the first preparedstatement after a period of inactivity: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure The last packet successfully received from the server was 2,855,054 milliseconds ago. The last packet sent successfully to the server was 123 milliseconds ago. at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source) at java.lang.reflect.Constructor.newInstance(Unknown Source) at com.mysql.jdbc.Util.handleNewInstance(Util.java:406) at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1074) at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3052) at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2938) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3481) at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1959) at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2109) at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2648) at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2077) at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:2228) This only shows up if my application hasn't communicated with MySQL recently. Subsequent queries execute normally. I suspect it's some kind of timeout issue, but the periods of inactivity are way below the 8 hour timeout for MySQL. Any suggestions?

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• Http 404: Not Found (WebException)

  - by Rajeev

  Hi, I am using a console app/class library to invoke a asp.net web service. The class library queries the database and sends the data to the web service. What I notice is that when the amount of data is huge (with 20 columns and 18K records), i get a HTTP 404: Not Found exception from the web service. I have tried increasing the maxReqeustLength and executionTimeout properties in the httpRuntime tag in the web.config of the web service. Is there any thing that I can do to overcome this? Thanks, Rajeev

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• Rails - how can I query the db w/o touching the sessions table

  - by sa125

  Hi - I'm trying to provide a HTTP api to my app that queries a db that's read-only (for replication purposes). I find that my app crashes repeatedly when making a request b/c the call is trying to update the sessions table whenever I query the db. This doesn't happen when I return some text without hitting the database for info. class APIController < AplicationController def view data = Product.find(params[:id]).to_json # will fail data = { :one => 1, :two => 2 }.to_json # will succeed respond_to do |format| format.html { render :json => data } end end end How do I restrict it from touching the sessions table on this request (it's currently issuing an UPDATE on the updated_at field for that session). thanks.

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• HTTP Cache Control max-age, must-revalidate

  - by nyb

  I have a couple of queries related to Cache-Control. If I specify Cache-Control "max-age=3600, must-revalidate" for a static html/js/images/css file, with Last Modified Header defined in HTTP header, a. Does browser/proxy cache(liek Squid/Akamai) go all the way to orgin server to validate before max-age expires? Or will it serve content from cache till max-age expires? b. After max-age expiry(that is expiry from cache), is there a IMS check or is content re-downloaded from origin server w/o IMS check?

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• custom MSSQL driver

  - by hoodoos

  I had a crazy thought about writing my own MSSQL driver to make it work something like non-blocking http client, so it won't be thread thirsty and could handle lots of db queries within one thread. I tried to look over google for some guidelines about implementing MSSQL client protocol, but found none really, where do those guys get information about it when they write own implementations for PHP or python? I need a really low level to be documented so I can implement all phases of working with a connection through sockets. And would be really nice to have a an example in c# langauge. :)

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• SSRS report combine data sources and generate csv

  - by Nithin

  I am new to ssrs. I have a report that gets data from two databases. I can create two datasets that connect to two different databases. The databases are third party and I cannot create stored procedures on the databases. My issue is that I have to combine the data from the two queries. Please help me with this issue or point me to locations where I can find answers. Thanks in advance.

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• Probability distribution for sms answer delays

  - by Thomas Ahle

  I'm writing an app using sms as communication. I have chosen to subscribe to an sms-gateway, which provides me with an API for doing so. The API has functions for sending as well as pulling new messages. It does however not have any kind of push functionality. In order to do my queries most efficient, I'm seeking data on how long time people wait before they answer a text message - as a probability function. Extra info: The application is interactive (as can be), so I suppose the times will be pretty similar to real life human-human communication. I don't believe differences in personal style will play a big impact on the right times and frequencies to query, so average data should be fine.

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• iPhone facebook connect FQL Query to get Profile URL.

  - by user306641

  Hai. I am using Face book Connect FQL Queries to extract my profile photo url that is src_big,src_small URL. But i am always getting the empty array in below delegate (void)request:(FBRequest*)request didLoad:(id)result My FQL query is. NSString* fql = [NSString stringWithFormat:@"SELECT src_big,src_small FROM photo WHERE pid IN (SELECT cover_pid FROM album WHERE owner =%lld AND name ='Profile Pictures')", session.uid]; NSDictionary* params = [NSDictionary dictionaryWithObject:fql forKey:@"query"]; [[FBRequest requestWithDelegate:self] call:@"facebook.fql.query" params:params]; But - (void)request:(FBRequest*)request didLoad:(id)result always return the empty result. Can any one please correct me if there any mistake.

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• Using MySQL as data source in Microsoft SQL Server Analysis Services

  - by coldilocks

  Hi, I have installed the latest .net connector (http://www.mysql.com/downloads/connector/net/), I can add MySQL databases as Data Sources, I can even browse through the data from Business Intelligence Studio. The problem is that I CANNOT create a datasource view, or if I do create one without tables, trying to add them after the fact gives me the same error. Specifically it looks like the data source view wizard tries to submit queries against the MySQL database using square brackets/braces, and the query bombs. I get an error message like: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '[my_db].[cheatType]' at line 2 So, in summary, has anyone been able to create a data source view using MySQL tables and, if so, can they please show me how this can be done. Thanks for any help!

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• Automating WebTrends analysis

  - by tridium

  Every week I access server logs processed by WebTrends (for about 7 profiles) and copy ad clickthrough and visitor information into Excel spreadsheets. A lot of it is just accessing certain sections and finding the right title and then copying the unique visitor information. I tried using WebTrends' built-in query tool but that is really poorly done (only uses a drag-and-drop system instead of text-based) and it has a maximum number of parameters and maximum length of queries to query with. As far as I know, the tools in WebTrends are not suitable to my purpose of automating the entire web metrics gathering process. I've gotten access to the raw server logs, but it seems redundant to parse that given that they are already being processed by WebTrends. To me it seems very scriptable, but how would I go about doing that? Is screen-scraping an option?

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• Array of previous weeks

  - by azz0r

  Hello, I am trying to create an array of weeks for users to select to view stats week on week. What I'm looking for is an array that has the timestamp of week start (monday 00.00 to sunday 11.59) that I can then use in MYSQL queries. Has anyone got an code that might assist? I was thinking of doing something like: $number_of_weeks = 4; $week_array = array(); foreach ($number_of_weeks as $week) { $number_of_weeks--; $value = $number_of_weeks * 604800; $StartOfLastWeek = 6 + date("w",mktime()); $week_array[$number_of_week]['start'] = date('Y-m-d', strtotime("-$StartOfLastWeek day"), $value); $week_array[$number_of_week]['end'] = date('Y-m-d', strtotime("-$StartOfLastWeek day"), $value+ 604800); }

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• Can this sql query be simplified?

  - by Bas

  I have the following tables: Person, {"Id", "Name", "LastName"} Sports, {"Id" "Name", "Type"} SportsPerPerson, {"Id", "PersonId", "SportsId"} For my query I want to get all the Persons that excersise a specific Sport whereas I only have the Sports "Name" attribute at my disposal. To retrieve the correct rows I've figured out the following queries: SELECT * FROM Person WHERE Person.Id in ( SELECT SportsPerPerson.PersonId FROM SportsPerPerson INNER JOIN Sports on SportsPerPerson.SportsId = Sports.Id WHERE Sports.Name = 'Tennis' ) AND Person.Id in ( SELECT SportsPerPerson.PersonId FROM SportsPerPerson INNER JOIN Sports on SportsPerPerson.SportsId = Sports.Id WHERE Sports.Name = 'Soccer' ) OR SELECT * FROM Person WHERE Id IN (SELECT PersonId FROM SportsPerPerson WHERE SportsId IN (SELECT Id FROM Sports WHERE Name = 'Tennis')) AND Id IN (SELECT PersonId FROM SportsPerPerson WHERE SportsId IN (SELECT Id FROM Sports WHERE Name = 'Soccer')) Now my question is, isn't there an easier way to write this query? Using just OR won't work because I need the person who play 'Tennis' AND 'Soccer'. But using AND also doesn't work because the values aren't on the same row.

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• Profiling statements inside a User-Defined Function

  - by Craig Walker

  I'm trying to use SQL Server Profiler (2005) to track down some application performance problems. One of the calls being made is to a table-valued user-defined function. This function wraps a select that joins several tables together. In SQL Server Profiler, the call to the UDF is logged. However, the select that underlies the UDF isn't being logged at all. Because of this, I'm not getting useful data on which tables & indexes are being hit. I'd like to feed this info into the Database Tuning Advisor for some indexing advice. Is there any way (short of unwrapping the queries themselves) to log the tables called by UDFs in Profiler?

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• Database on the fly with scripting languages

  - by afilatun

  I have a set of .csv files that I want to process. It would be far easier to process it with SQL queries. I wonder if there is some way to load a .csv file and use SQL language to look into it with a scripting language like python or ruby. Loading it with something similar to ActiveRecord would be awesome. The problem is that I don't want to have to run a database somewhere prior to running my script. I souldn't have additionnal installations needed outside of the scripting language and some modules. My question is which language and what modules should I use for this task. I looked around and can't find anything that suits my need. Is it even possible?

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• SQL-query task, decision?

  - by Sirius Lampochkin

  There is a table of currencies rates in MS SQL Server 2005: ID | CURR | RATE | DATE 1   | USD   | 30      | 01.10.2010 3   | GBP   | 45      | 07.10.2010 5   | USD   | 31      | 08.10.2010 7   | GBP   | 46      | 09.10.2010 9   | USD   | 32      | 12.10.2010 11 | GBP   | 48      | 03.10.2010 Rate are updated in real time and there are more than 1 billion rows in the table. It needs to write a SQL-query, wich will provide latest rates per each currency. My decision is: SELECT c.[id],c.[curr],c.[rate],c.[date] FROM [curr_rate] c, (SELECT curr, MAX(date) AS rate_date FROM [curr_rate] GROUP BY curr) t WHERE c.date = t.rate_date AND c.curr = t.curr ORDER BY c.[curr] ASC Is it possible to write a query without sub-queries and join's with derived tables?

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• Surgical slave reads for Ruby on Rails, mulitple databases.

  - by Daniel

  Greetings, I'm currently working on a multiple database rails application. I want to off load the SELECT queries on to the slave databases for only SOME of the databases or specific models. The issue is that in places, we swap out the current database connection and put in a different one for a short time; to load fixtures or to handle sharding. Does anyone have any recommendations on a ruby gem that 1. will split select/(sql writes) with a considerable amount of control. We want to handle just some models and we are looking for a neat surgical fix. 2. does not monkey around with activerecord. 3. is still being maintained. TIA -daniel

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• Would a Socket Connection Outperform an Intarvaled Database Sweep and Requests?

  - by Jascha

  I'm building a small chat application to add to an existing framework. There will only be 20-50 users MAX at any one time. I was wondering if I could get away with updating a cache file containing (semi) live chat data for whichever users happen to be chatting just by performing timed queries and regular AJAX refreshes for new data as opposed to learning how to open and maintain a socket connection. I'm sure there are existing chat plug-ins out there. But I just had a hell of a time installing one and I could see building the whole damn thing taking just as much time as plugging one in. Am I off to a bad start? Thanks in advance -J (p.s. this is a semi closed network behind a php login so security isn't a great concern)

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• Hibernate Subquery and DetachedCriteria

  - by dawez

  I have created a DetachedCriteria that is retrieving estates that have the isApproved and isPublished set to true. It is defined in this way: DetachedCriteria activePublishedCriteria = DetachedCriteria.forClass(Estate.class) .add(Restrictions.eq("isApproved", true)) .add(Restrictions.eq("isPublished", true)) .setResultTransformer(Criteria.DISTINCT_ROOT_ENTITY); I would like to reuse this criteria in some of the queries. In this case I would like to replace the isApproved and isPublished restrictions with the DetachedCriteria Criteria criteria = getSession().createCriteria(Estate.class) .createAlias("city", "c") .add(Restrictions.eq("c.id", cityID)) // the following 2 lines should be use the DetachedCriteria .add(Restrictions.eq("isApproved", true)) .add(Restrictions.eq("isPublished", true)) .setProjection(Projections.rowCount()); return (Integer) criteria.list().get(0); Is there a way to do this ? Tried to use .add.Subqueries.geAll(.... But cannot make it work properly. I could not find proper documentation on the Subqueries in Hibernate. Tips are welcomed.

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• How to pass the parameter in SQL query from PowerShell

  - by Zshava

  I have this code in PowerShell, that executes SQL query for UPDATE table: $Connection=new-object data.sqlclient.sqlconnection "server=server;database=mydb;trusted_connection=true;" $Connection.open() For( $i = 0; $i -le $ActID.Length; $i ++ ){ $cmd = New-Object System.Data.SqlClient.SqlCommand $cmd.Connection = $Connection $cmd.CommandText = " update Table set Note = @PATH " $cmd.Parameters.Add("@PATH", $ActID[$i].Values) | Out-Null $cmd.ExecuteNonQuery() } I try to update table with variable defined in this string: $cmd.Parameters.Add("@PATH", $ActID[$i].Values) | Out-Null But when i try to execute script, error log says that there is no value passed in $ActID[$i] Is there other methods to pass parameters (variables) in powershell queries?

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• MySql select by column value. Separeta operator for columns.

  - by andy

  Hi all, i have a mysql table like this +-----+---------+-----------+-----------------+-------+ | id | item_id | item_type | field_name | data | +-----+---------+-----------+-----------------+-------+ | 258 | 54 | page | field_interests | 1 | | 257 | 54 | page | field_interests | 0 | | 256 | 54 | page | field_author | value | +-----+---------+-----------+-----------------+-------+ And, I need build query like this SELECT * FROM table WHERE `field_name`='field_author' AND `field_author.data` LIKE '%jo%' AND `field_name`='field_interests' AND `field_interests.data`='0' AND `field_name`='field_interests' AND `field_interests.data`='1' This is sample query. MySql can't do queries like that. I mean than SELECT * FROM table WHERE name='jonn' AND name='marry' will return 0 rows. Cant anybody help me. Thanks.

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• How to improve INSERT INTO ... SELECT locking behavior

  - by Artem

  In our production database, we ran the following pseudo-code SQL batch query running every hour: INSERT INTO TemporaryTable (SELECT FROM HighlyContentiousTableInInnoDb WHERE allKindsOfComplexConditions are true) Now this query itself does not need to be fast, but I noticed it was locking up HighlyContentiousTableInInnoDb, even though it was just reading from it. Which was making some other very simple queries take ~25 seconds (that's how long that other query takes). Then I discovered that InnoDB tables in such a case are actually locked by a SELECT! http://www.mysqlperformanceblog.com/2006/07/12/insert-into-select-performance-with-innodb-tables/ But I don't really like the solution in the article of selecting into an OUTFILE, it seems like a hack (temporary files on filesystem seem sucky). Any other ideas? Is there a way to make a full copy of an InnoDB table without locking it in this way during the copy. Then I could just copy the HighlyContentiousTable to another table and do the query there.

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• Using one sqlconnection/sqlcommand through 2 DB-bound methods

  - by dotnetdev

  I have a class with a method which gets data from a database through a SELECT stored proc. This method uses a SqlDbReader by returning ExecuteReader() on a SqlCommand. The connection and everything is made in this method, with fields (such as connection string) set as class level fields. I now need to populate an array based on the results of this query (so the columns of each row will go into the array with its own index). However, this query will not select all of the data from one table which is involved. I can write the queries to get what I need, but how can I use one connection throughout the class? If I instantiate the connection object and call Open() in the constructor, I get an exception @ runtime. I'm hoping for something like this: // At class level: sqlconn.Open(); // sqlcommand set up Method() { // Fire stored proc // Insert results in a collection } Method2() { // Pass same collection in (use same one), // Add new row columns into same collection } How can I do this with strict performance in mind? Thanks

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• SQL Select Permissions

  - by Brandi

  I have a database that I need to connect to and select from. I have an SQL Login, let's call it myusername. When I use the following, no SELECT permission shows up: SELECT * FROM fn_my_permissions ('dbo.mytable', 'OBJECT') GO Several times I tried things like: USE mydatabase GO GRANT SELECT TO myusername GO GRANT SELECT ON DATABASE::mydatabase TO myusername GO GRANT SELECT ON mytable TO myusername GO It says the queries execute successfully, but there is never any difference in the first query. What simple thing am I missing to grant database level select permissions. As a note, I made double sure it was the correct user, correct database, and I have already tried granting table level select permissions. So far I keep getting the error: SELECT permission denied on object 'mytable', database 'mydatabase', schema 'dbo'. Any ideas what I'm missing? Thanks in advance.

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