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• LINQ - Linq to Sql - Specified cast is not valid - Please Help!

  - by thiag0

  I am trying to do the following... Request request = ( from r in db.Requests where r.Status == "Processing" && r.Locked == false select r).SingleOrDefault(); It is throwing the following exception... Message: Specified cast is not valid. StackTrace: at System.Data.Linq.SqlClient.SqlProvider.Execute(Expression query, QueryInfo queryInfo, IObjectReaderFactory factory, Object[] parentArgs, Object[] userArgs, ICompiledSubQuery[] subQueries, Object lastResult) at System.Data.Linq.SqlClient.SqlProvider.ExecuteAll(Expression query, QueryInfo[] queryInfos, IObjectReaderFactory factory, Object[] userArguments, ICompiledSubQuery[] subQueries) at System.Data.Linq.SqlClient.SqlProvider.System.Data.Linq.Provider.IProvider.Execute(Expression query) at System.Data.Linq.DataQuery`1.System.Linq.IQueryProvider.Execute[S](Expression expression) at System.Linq.Queryable.SingleOrDefault[TSource](IQueryable`1 source) at GDRequestProcessor.Worker.GetNextRequest() The .DBML file schema matches my database table that I am trying to select from so I have no clue why I am having this problem. Can anyone help me? Thanks in advance!

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• Copying Data between table without identity column

  - by user668479

  I have two table and I need to copy the data across from SRCServiceUsers to Clients Everytime i run it I get the following: Violation of PRIMARY KEY constraint 'PK_Clients'. Cannot insert duplicate key in object 'dbo.Clients'. The statement has been terminated. The Primary key ClientId field is not an identity column and therefore requires filling To date I have the following insert into Clients( ClientID, Title, Forenames, FamilyName, [Address], Town, County, PostCode, PhoneNumber, StartDate) SELECT ( Select Max(Clients.ClientID)+ 1, SRCServiceUsers.Title, SRCServiceUsers.[First Names], SRCServiceUsers.Surname, --BUILD UP MUITIPLE COLUMNS SRCServiceUsers.[Property Name] + ', ' + SRCServiceUsers.Street + ', ' + SRCServiceUsers.Suburb as [Address], SRCServiceUsers.Town, SRCServiceUsers.County, SRCServiceUsers.Postcode, SRCServiceUsers.Telephone, SRCServiceUsers.[Start Date] From srcsERVICEuSERS How can i autoincrement the PK field - CLientID when inserting the data? Many thanks Andrew

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• Find value of selected item in Drop down menu.

  - by Ozaki

  I have a drop down menu in an ASPX page along the lines of: <form> <select name="cars"> <option value="volvo">Volvo</option> <option value="saab">Saab</option> <option value="fiat" selected="selected">Fiat</option> <option value="audi">Audi</option> </select> </form> That is dynamically generated from another controller (value and label). After the user selects one of the options I need to find out what the selected value/label (will be the same) is so I can hit an update button and retrieve the data on that option. What would be the easiest way to find out the value of the user "selected" option?

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• In GWT-EXT checkboxtree how to handle single selection of tree nodes?

  - by RAS

  hi, I'm working on checkBoxTree in GWT-EXT 2.0.3 with Java. My aim is to get a selectionModel which allows me to select(check) only one TreeNode at a time. If I select another TreeNode after selecting one then, the previous one should be unchecked. I've tried using DefaultSelectionModel with TreePanel, but either I've not used it properly or it's working only for selection of TreeNode not for checking a TreeNode. Can anyone help me in this? Thanks in advance.

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• Filter across 2 lists using LINQ

  - by Ajit Goel

  I have two lists: a. requestedAmenities b. units with amenities. I want to filter those units that have any one of the "requested amenities". I have tried to achieve the same result using foreach loops but I believe it should be much easier using LINQ. Can someone please help\advice? UnitAmenities unitSearchRequestAmenities = unitSearchRequest.Amenities; var exactMatchApartmentsFilteredByAmenities= new Units(); IEnumerable<string> requestAmenitiesIds = unitSearchRequestAmenities.Select(element => element.ID); foreach (var unitCounter in ExactMatchApartments) { IEnumerable<string> unitAmenities = unitCounter.Amenities.Select(element => element.ID); foreach (var requestAmenityId in requestAmenitiesIds) { foreach (var unitAmenity in unitAmenities) { if (requestAmenityId == unitAmenity) { exactMatchApartmentsFilteredByAmenities.Add(unitCounter); //break to the outmost foreach loop } } } }

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• Advantage Data Architect doesn't accept 'output to', are there any other options for outputting a ta

  - by likesalmon

  I'm trying to output the results of a SELECT query to a tab delimited text file in Advantage Data Architect. I know I can use the 'Export to' feature to do this, but there are a lot of tables and that is going to take forever. I would rather use the SQL editor, but I found out it does not accept the OUTPUT TO argument, even though that command is part of Sybase SQL. I would like to do this: SELECT * FROM tablename; OUTPUT TO 'C:/ExportDirectory' DELIMITED BY '\t' FORMAT TEXT; Is there another way?

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• Why is doing a top(1) on an indexed column in SQL Server slow?

  - by reinier

  I'm puzzled by the following. I have a DB with around 10 million rows, and (among other indices) on 1 column (campaignid_int) is an index. Now I have 700k rows where the campaignid is indeed 3835 For all these rows, the connectionid is the same. I just want to find out this connectionid. use messaging_db; SELECT TOP (1) connectionid FROM outgoing_messages WITH (NOLOCK) WHERE (campaignid_int = 3835) Now this query takes approx 30 seconds to perform! I (with my small db knowledge) would expect that it would take any of the rows, and return me that connectionid If I test this same query for a campaign which only has 1 entry, it goes really fast. So the index works. How would I tackle this and why does this not work? edit: estimated execution plan: select (0%) - top (0%) - clustered index scan (100%)

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• Converting MySQL Resultset from Rows to Columns

  - by gms8994

  I have output from a select like this: 04:47:37> select * from attributes left outer join trailer_attributes on attributes.id = trailer_attributes.attribute_id; +----+--------------+----------+-----------+------------+--------------+-----------------+ | id | name | datatype | list_page | trailer_id | attribute_id | attribute_value | +----+--------------+----------+-----------+------------+--------------+-----------------+ | 1 | Make | text | 1 | 1 | 1 | Apple | | 1 | Make | text | 1 | 2 | 1 | sdfg | | 2 | Year | number | 1 | 1 | 2 | 2009 | | 2 | Year | number | 1 | 2 | 2 | sdfg | | 3 | Type | text | 0 | 1 | 3 | iPhone | | 3 | Type | text | 0 | 2 | 3 | sdfg | | 4 | Axles | text | 0 | 1 | 4 | asdf | | 4 | Axles | text | 0 | 2 | 4 | sdfg | | 7 | Size | text | 0 | 1 | 7 | asd1 | | 7 | Size | text | 0 | 2 | 7 | sdfg | | 8 | Frame | text | 0 | 1 | 8 | | | 8 | Frame | text | 0 | 2 | 8 | sdfg | | 9 | Height | text | 0 | 1 | 9 | | | 9 | Height | text | 0 | 2 | 9 | sdfg | | 10 | Dollies | text | 0 | 1 | 10 | | | 10 | Dollies | text | 0 | 2 | 10 | sdfg | | 11 | Tires/Wheels | text | 0 | 1 | 11 | | | 11 | Tires/Wheels | text | 0 | 2 | 11 | sdfg | | 12 | Condition | text | 1 | 1 | 12 | New | | 12 | Condition | text | 1 | 2 | 12 | sdfg | | 13 | Title | text | 0 | 1 | 13 | | | 13 | Title | text | 0 | 2 | 13 | sdfg | +----+--------------+----------+-----------+------------+--------------+-----------------+ I want to convert it to something more along the lines of: id, Make, Year, Type, Axles, Size, Frame (etc) 1, Apple, 2009, iPhone, ..... 2, sdfg, sdfg, sdfg, ..... Any suggestions?

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• Some facebook friends' birthdays returning as null but I have the correct API permissions

  - by Andrei Radulescu

  I'm tring to get my friends' birthdays in my app and some of them are null. I thought that those people don't have a birthday set, but they actually do. My fql query is: SELECT uid,name,birthday_date FROM user WHERE uid IN (SELECT uid2 from friend where uid1=me()) My app has the "friends_birthday" permission set. I also tried with "birthday" instead of "birthday_date". Same result. I imagine that this happens because they opted out somehow, but I don't know how. Is there an alternate solution to actually get their birthdays from facebook? Thanks!

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• A question about indexes regarding to the gain of inserts & updates in database

  - by Mestika

  Hi, I’m having a question about the fine line between the gain of an index to a table there is growing steadily in size every month and the gain of queries with an index. The situation is, that I’ve two tables, Table1 and Table2. Each table grows slowly but regularly each month (with about 100 new rows for Table1 and a couple of rows for Table2). My concrete question is whether to have an index or to drop it. I’ve made some measurement that an covering index on Table2 improve my SELECT queries and some rather much but again, I’ve to consider the pros and cons but having a really hard time to decide. For Table1 it might not be necessary to have an index because the SELECT queries there is not that common. I would appreciate any suggestion, tips or just good advice to what is a good solution. By the way, I’m using IBM DB2 version 9.7 as my Database system Sincerely Mestika

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• modx revo snippet variable in query

  - by Meddie

  I noticed something weird when using a query in a snippet. When I have a query like this: $sql = 'SELECT * FROM table WHERE colomn = ' . $variable; And I echo $sql, the query reads: SELECT * FROM table WHERE colomn = <code class="php plain">2</code> .. wich will result in an error because the sql is no longer valid. So for now I use strip_tags to remove the code tag, but I find it not a very clean method. I couldnt find anything about this, so maybe someone can shed some light on this for me?

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• Powershell Replace Regex

  - by Brad

  I have a select-string which is seaching an IIS log for a particular string and returning the 2 lines above and one line below. So results look like this: 2012-06-15 18:26:09 98.138.206.39 OutboundConnectionResponse SMTPSVC1 WEB10 - 25 - - 220+mta1083.sbc.mail.ne1.yahoo.com+ESMTP+YSmtp+service+ready 0 0 60 0 218 SMTP - - - - 2012-06-15 18:26:09 98.138.206.39 OutboundConnectionCommand SMTPSVC1 WEB10 - 25 EHLO - WEB10.DOMAINCOM 0 0 4 0 218 SMTP - - - - 2012-06-15 18:26:09 74.125.244.10 OutboundConnectionResponse SMTPSVC1 WEB10 - 25 - - 550+IP+Authorization+check+failed+-+psmtp 0 0 41 0 218 SMTP - - - - 2012-06-15 18:26:09 74.125.244.10 OutboundConnectionCommand SMTPSVC1 WEB10 - 25 RSET - - 0 0 4 0 218 SMTP - - - - Note the third line begins with denoting thats the line that select-string matched upon. I am trying to do a -replace on the to replace it with < font color="red"$1< /font but my replace doesn't seem to work. Here's my code: $results = $results -replace "(^ )(.*)$", "< font color='red'$1< font" Can any powershell regex guru's out there tell me why my regular expression isn't matching? Thanks Brad

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• How to cache queries in EJB and return result efficient (performance POV)

  - by Maxym

  I use JBoss EJB 3.0 implementation (JBoss 4.2.3 server) At the beginning I created native query all the time using construction like Query query = entityManager.createNativeQuery("select * from _table_"); Of couse it is not that efficient, I performed some tests and found out that it really takes a lot of time... Then I found a better way to deal with it, to use annotation to define native queries: @NamedNativeQuery( name = "fetchData", value = "select * from _table_", resultClass=Entity.class ) and then just use it Query query = entityManager.createNamedQuery("fetchData"); the performance of code line above is two times better than where I started from, but still not that good as I expected... then I found that I can switch to Hibernate annotation for NamedNativeQuery (anyway, JBoss's implementation of EJB is based on Hibernate), and add one more thing: @NamedNativeQuery( name = "fetchData2", value = "select * from _table_", resultClass=Entity.class, readOnly=true) readOnly - marks whether the results are fetched in read-only mode or not. It sounds good, because at least in this case of mine I don't need to update data, I wanna just fetch it for report. When I started server to measure performance I noticed that query without readOnly=true (by default it is false) returns result with each iteration better and better, and at the same time another one (fetchData2) works like "stable" and with time difference between them is shorter and shorter, and after 5 iterations speed of both was almost the same... The questions are: 1) is there any other way to speed query using up? Seems that named queries should be prepared once, but I can't say it... In fact if to create query once and then just use it it would be better from performance point of view, but it is problematic to cache this object, because after creating query I can set parameters (when I use ":variable" in query), and it changes query object (isn't it?). well, is here any way to cache them? Or named query is the best option I can use? 2) any other approaches how to make results retrieveng faster. I mean, for instance I don't need those Entities to be attached, I won't update them, all I need is just fetch collection of data. Maybe readOnly is the only available way, so I can't speed it up, but who knows :) P.S. I don't ask about DB performance, all I need now is how not to create query all the time, so use it efficient, and to "allow" EJB to do less job with the same result concerning data returning.

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• Mysql table data problem?

  - by DaTeNtImE

  I'm new to mysql and was wondering how can I add the users birthdate in the following HTML format to the MYSQL table data listed below? How would the structure look like for example email VARCHAR(80) NOT NULL,? Here is the HTML code below. <li><label>Date of Birth: </label> <label for="month">Month: </label> <select name="month" id="month"> <option value="January">January</option> <option value="February">February</option> <option value="March">March</option> <option value="April">April</option> <option value="May">May</option> <option value="June">June</option> <option value="July">July</option> <option value="August">August</option> <option value="September">September</option> <option value="October">October</option> <option value="November">November</option> <option value="December">December</option> </select> <label for="day">Day: </label> <select id="day" name="day"> <option value="0" selected="selected">Day</option> <option value="1">1</option> <option value="2">2</option> <option value="3">3</option> <option value="4">4</option> <option value="5">5</option> <option value="6">6</option> <option value="7">7</option> <option value="8">8</option> <option value="9">9</option> <option value="10">10</option> <option value="11">11</option> <option value="12">12</option> <option value="13">13</option> <option value="14">14</option> <option value="15">15</option> <option value="16">16</option> <option value="17">17</option> <option value="18">18</option> <option value="19">19</option> <option value="20">20</option> <option value="21">21</option> <option value="22">22</option> <option value="23">23</option> <option value="24">24</option> <option value="25">25</option> <option value="26">26</option> <option value="27">27</option> <option value="28">28</option> <option value="29">29</option> <option value="30">30</option> <option value="31">31</option> </select> <label for="year">Year: </label><input type="text" name="year" id="year" /></li> Here is the MySQL table data. CREATE TABLE users ( user_id INT UNSIGNED NOT NULL AUTO_INCREMENT, first_name VARCHAR(20) NOT NULL, last_name VARCHAR(40) NOT NULL, email VARCHAR(80) NOT NULL, pass CHAR(40) NOT NULL, user_level TINYINT(1) UNSIGNED NOT NULL DEFAULT 0, active CHAR(32), registration_date DATETIME NOT NULL, PRIMARY KEY (user_id), UNIQUE KEY (email), INDEX login (email, pass) );

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• Jquery taconite selector with character that needs to be escaped

  - by hdx

  I'm using the jquery taconite plugin to make an ajax request that will replace a certain element in my page, however the element has an id like "email.subject".. I can select it just fine if I do '$("email\\.subject")', but when I try to use the taconite plugin like this: <taconite> <replaceWith select="#email\\.subject"> JUCA </replaceWith> </taconite> The plugin log says: [taconite] No matching targets for selector: #email\\.subject How can I make this work?

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• bytea type & nulls, Postgres

  - by Thanatos

  I'm using a bytea type in PostgreSQL, which, to my understanding, contains just a series of bytes. However, I can't get it to play well with nulls. For example: =# select length(E'aa\x00aa'::bytea); length -------- 2 (1 row) I was expecting 5. Also: =# select md5(E'aa\x00aa'::bytea); md5 ---------------------------------- 4124bc0a9335c27f086f24ba207a4912 (1 row) That's the MD5 of "aa", not "aa\x00aa". Clearly, I'm Doing It Wrong, but I don't know what I'm doing wrong. I'm also on an older version of Postgres (8.1.11) for reasons outside of my control. (I'll see if this behaves the same on the latest Postgres as soon as I get home...)

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• CKEditor plugin: Hightlight selected text by hovering on a new item in the toolbar and selecting fro

  - by scottystang

  I'm new to the CKEditor and I'm trying to create a simple plugin. What I'm hoping to accomplish is to allow the user to highlight some text and then hover on a new item in the toolbar that drops down on mouse over a few different highlight color options for the text. For example, the user could highlight some text, hover on my new item and then select a highlight color. This will be similar to the 'BGColor' plugin except instead of opening a color palette to choose from, the user would select from a drop down of options similar to when you choose to change the font size you have a list of options such as '10', '11', '12', etc. Any help would be appreciated on how to pull this off. I was hoping to check out how 'BGColor' and 'FontSize' plugins where implemented, but I can't find these in ../ckeditor/_source/plugins. Am I looking in the right spot? Also, the link for plugins here - http://docs.cksource.com/CKEditor_3.x/Developers_Guide isn't clickable so I'm not sure if there's a place for plugin documentation that I can check out.

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• Unable to jump to row 0 on MySQL result index 13

  - by Ahmet Kemal

  What is the reason of the error on title? My script is below. Thank you. $fbFoodPerma = $fbSiteID."-".$fbFoodPerma; $sql = mysql_query(" SELECT fbFoodPerma FROM fbFoods WHERE fbFoodPerma LIKE '$fbFoodPerma'") or die(mysql_error()); $isStored = mysql_result($sql,0,"fbFoodPerma"); while ($isStored == "$fbFoodPerma") { $fbFoodPerma = $fbFoodPerma."-"; $sql = mysql_query(" SELECT fbFoodPerma FROM fbFoods WHERE fbFoodPerma LIKE '$fbFoodPerma'") or die(mysql_error()); $isStored = mysql_result($sql,0,"fbFoodPerma"); }

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• jQuery get value from checked element with a given name

  - by Travis Leleu

  I've got an input like so: I'd like to use jQuery to grab that element, and add the function call foo() to the change event. Currently I can get it done, but there are two hacks involved. My (working) code: $(":input[name*=myfield]").change( function( $(":input[name*=myfield]") ) { foo(); }); )}; There are two hacks in there I'd like to eliminate. Keeping in mind that the input names are multidimensional arrays, how can I use the :input[name=somename], versus [name*=someone]? I'd imagine it's faster using an exact name rather than *=, but I can't get the escape sequence correct for the brackets on the multidimensional arrays. Can I chain the call together so that I don't have to select the element twice? Is the standard practice for that to select the HTML element into a var, then use that var? Or can I chain it together? Thanks for the help. Still working on getting my footing in JS/JQ.

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• Multiple Class in JDO Query

  - by Dan Delgado

  Hello, I'm currently developing in GAE and I have to query like this using JDO: SELECT table1.column1, table2.column2 FROM table1, table2 WHERE table1.column1 = table2.column1; I tried this one but it won't work: String query = "select from "+Assessment.class.getName()+ "a, "+ Project.class.getName()+" p where a.projectId == p.id && p.owner=='"+owner+"'"; Is this valid or this really isn't supported yet? If this is valid, why is it not working then? If it isn't, what should I do to make this work? Thank you!

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• T-SQL to PL/SQL (IDENTITY)

  - by folone

  I've got a T-SQL script, that converts field to IDENTITY (in a weird way). How do I convert it to PL/SQL? (and, probably, figure out, if there is a simpler way to do this - without creating a temporary table). The T-SQL script: -- alter table ts_changes add TS_THREADID VARCHAR(100) NULL; -- Change Field TS_ID TS_NOTIFICATIONEVENTS to IDENTITY BEGIN TRANSACTION GO CREATE TABLE dbo.Tmp_TS_NOTIFICATIONEVENTS ( TS_ID int NOT NULL IDENTITY (1, 1), TS_TABLEID int NOT NULL, TS_CASEID int NULL, TS_WORKFLOWID int NULL, TS_NOTIFICATIONID int NULL, TS_PRIORITY int NULL, TS_STARTDATE int NULL, TS_TIME int NULL, TS_WAITSTATUS int NULL, TS_RECIPIENTID int NULL, TS_LASTCHANGEDATE int NULL, TS_ELAPSEDCYCLES int NULL ) ON [PRIMARY] SET IDENTITY_INSERT dbo.Tmp_TS_NOTIFICATIONEVENTS ON GO IF EXISTS(SELECT * FROM dbo.TS_NOTIFICATIONEVENTS) EXEC('INSERT INTO dbo.Tmp_TS_NOTIFICATIONEVENTS (TS_ID, TS_TABLEID, TS_CASEID, TS_WORKFLOWID, TS_NOTIFICATIONID, TS_PRIORITY, TS_STARTDATE, TS_TIME, TS_WAITSTATUS, TS_RECIPIENTID, TS_LASTCHANGEDATE, TS_ELAPSEDCYCLES) SELECT TS_ID, TS_TABLEID, TS_CASEID, TS_WORKFLOWID, TS_NOTIFICATIONID, TS_PRIORITY, TS_STARTDATE, TS_TIME, TS_WAITSTATUS, TS_RECIPIENTID, TS_LASTCHANGEDATE, TS_ELAPSEDCYCLES FROM dbo.TS_NOTIFICATIONEVENTS WITH (HOLDLOCK TABLOCKX)') GO SET IDENTITY_INSERT dbo.Tmp_TS_NOTIFICATIONEVENTS OFF GO DROP TABLE dbo.TS_NOTIFICATIONEVENTS GO EXECUTE sp_rename N'dbo.Tmp_TS_NOTIFICATIONEVENTS', N'TS_NOTIFICATIONEVENTS', 'OBJECT' GO ALTER TABLE dbo.TS_NOTIFICATIONEVENTS ADD CONSTRAINT aaaaaTS_NOTIFICATIONEVENTS_PK PRIMARY KEY NONCLUSTERED ( TS_ID ) WITH( STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] GO COMMIT

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• MySQL Count If using 4 tables or Perl

  - by user1726133

  Hi I have a relatively convoluted query that relies on 4 different tables, unfortunately I do not have control of this data, but I do have to query it. I ran this simpler query and it works using just table 1 and table 2 SELECT actor, receiver, count(IF(t2.group1 = "anxiety behavior", 1,0)) AS 'anxiety' FROM ethogram_edited_obs_behaviors t1 JOIN ethogram_behaviors t2 on t1.behavior = t2.behavior_code GROUP BY actor; Below are the 4 tables I need and the query I tried that didn't work Table 1 | Table 2 | Table 3 | Table 4 Actor | Behavior | Behavior | type of Behavior | subject | sex | subject |subject_code er frown | frown anxiety behavior | Eric M | Eric | er Here is the query that is failing SELECT actor, count(IF(t2.group1 = "anxiety behavior", 1,0) AND(t3.sex = "M", 1,0)) AS 'anxiety', FROM ethogram_edited_obs_behaviors t1 JOIN ethogram_behaviors t2 on t1.behavior = t2.behavior_code JOIN subject_code t3 on t1.actor = t3.behavior_code1 JOIN subjects t4 on t3.subject = t4.yerkes_code GROUP BY actor; Any help would be much appreciated!! Thanks :) P.S. if this is easier to do in Perl tips also much appreciated

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• SQL query duration is longer for smaller dataset?

  - by entens

  I received reports that a my report generating application was not working. After my initial investigation, I found that the SQL transaction was timing out. I'm mystified as to why the query for a smaller selection of items would take so much longer to return results. Quick query (averages 4 seconds to return): SELECT * FROM Payroll WHERE LINEDATE >= '04-17-2010'AND LINEDATE <= '04-24-2010' ORDER BY 'EMPLYEE_NUM' ASC, 'OP_CODE' ASC, 'LINEDATE' ASC Long query (averages 1 minute 20 seconds to return): SELECT * FROM Payroll WHERE LINEDATE >= '04-18-2010'AND LINEDATE <= '04-24-2010' ORDER BY 'EMPLYEE_NUM' ASC, 'OP_CODE' ASC, 'LINEDATE' ASC I could simply increase the timeout on the SqlCommand, but it doesn't change the fact the query is taking longer than it should. Why would requesting a subset of the items take longer than the query that returns more data? How can I optimize this query?

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• Nesting queries in SQL

  - by ZAX

  The goal of my query is to return the country name and its head of state if it's headofstate has a name starting with A, and the capital of the country has greater than 100,000 people utilizing a nested query. Here is my query: SELECT country.name as country, (SELECT country.headofstate from country where country.headofstate like 'A%') from country, city where city.population > 100000; I've tried reversing it, placing it in the where clause etc. I don't get nested queries. I'm just getting errors back, like subquery returns more than one row and such. If someone could help me out with how to order it, and explain why it needs to be a certain way, that'd be great.

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• Rails/mysql SUM distinct records - optimization

  - by pepernik

  Hey. How would you optimize this SQL SELECT SUM(tmp.cost) FROM ( SELECT DISTINCT clients.id as client, countries.credits_cost AS cost FROM countries INNER JOIN clients ON clients.country_id = countries.id INNER JOIN clients_groups ON clients_groups.client_id=clients.id WHERE clients_groups.group_id IN (1,2,3,4,5,6,7,8,9) GROUP BY clients.id ) AS tmp; I'm using this example as part of my Ruby on Rails project. Note that my nested SQL (tmp) can have more then 10 milion records. You can split that in more SQLs if the performance is better. Should I add any indexes to make it quicker (i have it on IDs)?

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