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• Getting counts of 0 from a query with a double group by

  - by Maltiriel

  I'm trying to write a query that gets the counts for a table (call it item) categorized by two different things, call them type and code. What I'm hoping for as output is the following: Type Code Count 1 A 3 1 B 0 1 C 10 2 A 0 2 B 13 2 C 2 And so forth. Both type and code are found in lookup tables, and each item can have just one type but more than one code, so there's also a pivot (aka junction or join) table for the codes. I have a query that can get this result: Type Code Count 1 A 3 1 C 10 2 B 13 2 C 2 and it looks like (with join conditions omitted): SELECT typelookup.name, codelookup.name, COUNT(item.id) FROM typelookup LEFT OUTER JOIN item JOIN itemcodepivot RIGHT OUTER JOIN codelookup GROUP BY typelookup.name, codelookup.name Is there any way to alter this query to get the results I'm looking for? This is in MySQL, if that matters. I'm not actually sure this is possible all in one query, but if it is I'd really like to know how. Thanks for any ideas.

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• I'm asked to tune a long starting app into a short time period

  - by Jason

  Hi, I'm asked to shorten the startup period of a long starting app, however I have also to obligate to my managers to the amount of time i will reduce the startup - something like 10-20 seconds. As i'm new in my company I said I can obligate with timeframe of months (its a big server and I'm new and i plan to do lazy load + performance tuning). that answer was not accepted I was required to do some kind of a cache to hold important data in another server and then when my server starts up it would reach all its data from that cache - I find it a kind of a workaround and i don't really like it. do you like it? what do you think I should do? any suggestions? PS when i profiled the app i saw many small issues that make the startup long (like 2 minutes) it would not be a short process to fix all and to make lazy load. Any kind of suggestions would help. language - java. Thanks

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• MySQL customized join query using multiple tables

  - by itgeek

  I am searching one student from each class from one group. There are different class groups and every group has different classes and every class has multiple students. See below: Group1 --> Class1, Class2 etc Class1 --> GreenStudent1, GreenStudent2 etc Class2 --> RedStudent1, RedStudent2 etc ------------------------------------------------------ SELECT table1.id, table1.myname, table1.marks table2.studentid, table2.studentname FROM table1 INNER JOIN table3 ON table1.oldid = table3.id INNER JOIN table2 ON table2.studentid = table3.newid WHERE table1.classgroup = 'SCI79' GROUP BY table1.oldid ORDER BY table1.marks DESC There are different joins applied in the query. Above mentioned query giving me correct results but I need little modification in it. Current query returning me one student from each class. What I need? I need one student from each class but only that student who has MAXIMUM table1.marks So I should have one student from each class who has maximum number in their relevant classes. Can anyone suggest some solution or rewrite this query? Thanks :)

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• Get the first and last posts in a thread

  - by Grampa

  I am trying to code a forum website and I want to display a list of threads. Each thread should be accompanied by info about the first post (the "head" of the thread) as well as the last. My current database structure is the following: threads table: id - int, PK, not NULL, auto-increment name - varchar(255) posts table: id - int, PK, not NULL, auto-increment thread_id - FK for threads The tables have other fields as well, but they are not relevant for the query. I am interested in querying threads and somehow JOINing with posts so that I obtain both the first and last post for each thread in a single query (with no subqueries). So far I am able to do it using multiple queries, and I have defined the first post as being: SELECT * FROM threads t LEFT JOIN posts p ON t.id = p.thread_id ORDER BY p.id LIMIT 0, 1 The last post is pretty much the same except for ORDER BY id DESC. Now, I could select multiple threads with their first or last posts, by doing: SELECT * FROM threads t LEFT JOIN posts p ON t.id = p.thread_id ORDER BY p.id GROUP BY t.id But of course I can't get both at once, since I would need to sort both ASC and DESC at the same time. What is the solution here? Is it even possible to use a single query? Is there any way I could change the structure of my tables to facilitate this? If this is not doable, then what tips could you give me to improve the query performance in this particular situation?

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• Very Different Execution Times of SQL Query in C# and SQL Server Management Studio

  - by Paul

  I have a simple SQL query that when run from C# takes over 30 seconds then times-out every time, whereas when run on SQL Server Management Studio successfully completes instantly. In the latter case, a query execution plan reveals nothing troubling, and the execution time is spread nicely through a few simple operations. I've run 'EXEC sp_who2' while the query is running from C#, and it is listed as taking 29,000 milliseconds of CPU time, and is not blocked by anything. I have no idea how to begin solving this. Does anyone have some insight? The query is: SELECT c.lngId, ... FROM tblCase c INNER JOIN tblCaseStatus s ON s.lngId = c.lngId INNER JOIN tblCaseStatusType t ON t.lngId = s.lngId INNER JOIN [Another Database]..tblCompany cm ON cm.lngId = cs.lngCompanyId WHERE t.lngId = 25 AND c.IsDeleted = 0 AND s.lngStatus = 1

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• Why I can't use template table in dynamic query SQL SERVER 2005

  - by StuffHappens

  Hello! I have the following t-sql code which generates an error Declare @table TABLE ( ID1 int, ID2 int ) INSERT INTO @table values(1, 1); INSERT INTO @table values(2, 2); INSERT INTO @table values(3, 3); DECLARE @field varchar(50); SET @field = 'ID1' DECLARE @query varchar(MAX); SET @query = 'SELECT * FROM @table WHERE ' + @field + ' = 1' EXEC (@query) The error is Must declare the table variable "@table". What's wrong with the query. How to fix it?

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• CAML query soap SharePoint

  - by robScott

  I'm trying to access a SharePoint list and return the calendar dates for a custom webpart I made. It was working fine, then I decided to only retrieve the date selected rather than the whole calendar, so I wanted to add a where clause. I've tried 'yyyy-MM-dd', 'yyyy-MM-ddThh:mm:ssZ', and 'yyyy-MM-dd hh:mm:ssZ' as string formats I've also tried MM/dd/yyyy as a date format. I'm using jQuery, and I do have list items in the calendar. I'm assuming my date is not in the correct format. var date = $(this).attr('date'); var sharepointDate = Date.parse(date).toString('yyyy-mm-ddT00:00:01Z'); var soapEnv = "<soapenv:Envelope xmlns:soapenv='http://schemas.xmlsoap.org/soap/envelope/'> \ <soapenv:Body> \ <GetListItems xmlns='http://schemas.microsoft.com/sharepoint/soap/'> \ <listName>CorporateCalendar</listName> \ <viewFields> \ <ViewFields> \ <FieldRef Name='Title' /> \ </ViewFields> \ </viewFields> \ <query><Query><Where><Geq><FieldRef Name='EventDate' /><Value Type='DateTime'>" + sharepointDate + "</Value></Geq></Where></Query></query> \ <rowLimit>500</rowLimit> \ </GetListItems> \ </soapenv:Body> \ </soapenv:Envelope>"; If I take the where clause out I receive all the items in the calendar. If the query is in there, I receive no results. Thanks in advance

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• Scalable way of doing self join with many to many table

  - by johnathan

  I have a table structure like the following: user id name profile_stat id name profile_stat_value id name user_profile user_id profile_stat_id profile_stat_value_id My question is: How do I evaluate a query where I want to find all users with profile_stat_id and profile_stat_value_id for many stats? I've tried doing an inner self join, but that quickly gets crazy when searching for many stats. I've also tried doing a count on the actual user_profile table, and that's much better, but still slow. Is there some magic I'm missing? I have about 10 million rows in the user_profile table and want the query to take no longer than a few seconds. Is that possible?

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• MySQL Single Query Benchmarking Strategies

  - by Pepper

  Hello, I have a slow mySQL query in my application that I need to re-write. The problem is, it's only slow on my production server and only when it's not cached. The first time I run it, it will take 12 seconds, then anytime after that it'll be 500 milliseconds. Is there an easy way to test this query without it hitting the query cache so I can see the results of my refactoring? Thanks!

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• Need to use query column value in nested subquery

  - by Dustin

  It seems I cannot use a column from the parent query in a sub query. How can I refactor this query to get what I need? dbo.func_getRelatedAcnts returns a table of related accounts (all children from a given account). Events and Profiles are related to accounts. SELECT COUNT(r.reg_id) FROM registrations r JOIN profiles p ON (r.reg_frn_pro_id = p.pro_id) JOIN events e ON (r.reg_frn_evt_id = e.evt_id) WHERE evt_frn_acnt_id NOT IN (SELECT * FROM dbo.func_getRelatedAcnts(p.pro_frn_acnt_id))

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• mysql syntax how to add a third table to $query

  - by IberoMedia

  I have code: $query = "SELECT a.*, c.name as categoryname, c.id as categoryid". " FROM #__table_one as a". " LEFT JOIN #__table_two c ON c.id = a.catid"; $query .= " WHERE a.published = 1" ." AND a.access <= {$aid}" ." AND a.trash = 0" ." AND c.published = 1" ." AND c.access <= {$aid}" ." AND c.trash = 0" ; I would like to add a third table ('__some_table') for the parts of the query where a.publish, a.access and a.trash. In other words, I want these fields to be retrieved from another table, not "#__table_one", but I do not know how to incorporate the #__some_table into the current query I imagine the JOIN command can help me, but I do not know how to code mysql Thank you,

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• Efficiently select top row for each category in the set

  - by VladV

  I need to select a top row for each category from a known set (somewhat similar to this question). The problem is, how to make this query efficient on the large number of rows. For example, let's create a table that stores temperature recording in several places. CREATE TABLE #t ( placeId int, ts datetime, temp int, PRIMARY KEY (ts, placeId) ) -- insert some sample data SET NOCOUNT ON DECLARE @n int, @ts datetime SELECT @n = 1000, @ts = '2000-01-01' WHILE (@n>0) BEGIN INSERT INTO #t VALUES (@n % 10, @ts, @n % 37) IF (@n % 10 = 0) SET @ts = DATEADD(hour, 1, @ts) SET @n = @n - 1 END Now I need to get the latest recording for each of the places 1, 2, 3. This way is efficient, but doesn't scale well (and looks dirty). SELECT * FROM ( SELECT TOP 1 placeId, temp FROM #t WHERE placeId = 1 ORDER BY ts DESC ) t1 UNION ALL SELECT * FROM ( SELECT TOP 1 placeId, temp FROM #t WHERE placeId = 2 ORDER BY ts DESC ) t2 UNION ALL SELECT * FROM ( SELECT TOP 1 placeId, temp FROM #t WHERE placeId = 3 ORDER BY ts DESC ) t3 The following looks better but works much less efficiently (30% vs 70% according to the optimizer). SELECT placeId, ts, temp FROM ( SELECT placeId, ts, temp, ROW_NUMBER() OVER (PARTITION BY placeId ORDER BY ts DESC) rownum FROM #t WHERE placeId IN (1, 2, 3) ) t WHERE rownum = 1 The problem is, during the latter query execution plan a clustered index scan is performed on #t and 300 rows are retrieved, sorted, numbered, and then filtered, leaving only 3 rows. For the former query three times one row is fetched. Is there a way to perform the query efficiently without lots of unions?

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• Zend Database Adapter - Complex MySQL Query

  - by Sonny

  I have defined a function in my Navigation model that executes a query, and I was wondering if there's a more "Zendy" way of generating/executing the query. The query I'm using was proposed by Bill Karwin on another thread here for setting arbitrary record order. I tried using a prepared statement, but the values in the SIGN() function got quoted. I'm using the PDO adapter for MySQL. /** * */ public function setPosition($parentId, $oldPosition, $newPosition) { $parentId = intval($parentId); $oldPosition = intval($oldPosition); $newPosition = intval($newPosition); $this->getAdapter()->query(" UPDATE `navigation` SET `position` = CASE `position` WHEN $oldPosition THEN $newPosition ELSE `position` + SIGN($oldPosition - $newPosition) END WHERE `parent_id` = $parentId AND `position` BETWEEN LEAST($oldPosition, $newPosition) AND GREATEST($oldPosition, $newPosition) "); return $this; }

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• Python: Time a code segment for testing performance (with timeit)

  - by Mestika

  Hi, I've a python script which works just as it should but I need to write the time for the execution. I've gooled that I should use timeit but I can't seem to get it to work. My Python script looks like this: import sys import getopt import timeit import random import os import re import ibm_db import time from string import maketrans myfile = open("results_update.txt", "a") for r in range(100): rannumber = random.randint(0, 100) update = "update TABLE set val = %i where MyCount >= '2010' and MyCount < '2012' and number = '250'" % rannumber #print rannumber conn = ibm_db.pconnect("dsn=myDB","usrname","secretPWD") for r in range(5): print "Run %s\n" % r ibm_db.execute(query_stmt) query_stmt = ibm_db.prepare(conn, update) myfile.close() ibm_db.close(conn) What I need it the time it takes the execution of the query and written to the file "results_update.txt". The purpose is to test an update statement for my database with different indexes and tuning mechanisms. Sincerely Mestika

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• Query Becnhmark.

  - by Deepika

  I am using autobech for doing becnhmark. An example of autobench command is as shown below. autobench --single_host --host1 testhost.foo.com --uri1 /index.html --quiet --timeout 5 --low_rate 20 --high_rate 200 --rate_step 20 --num_call 10 --num_conn 5000 --file bench.tsv The uri which I have to specify has a query attached to it. When I run the command which has the query, I get the following result dem_req_rate req_rate_localhost con_rate_localhost min_rep_rate_localhost avg_rep_rate_localhost max_rep_rate_localhost stddev_rep_rate_localhost resp_time_localhost net_io_localhost errors_localhost 200 0 20 0 0 0 0 0 0 101 400 0 40 0 0 0 0 0 0 101 600 0 60 0 0 0 0 0 0 101 800 0 80 0 0 0 0 0 0 101 1000 0 100 0 0 0 0 0 0 101 1200 0 120 0 0 0 0 0 0 101 1400 0 140 0 0 0 0 0 0 101 1600 0 160 0 0 0 0 0 0 101 1800 0 180 0 0 0 0 0 0 101 2000 0 200 0 0 0 0 0 0 101 The query request, response are all zeroes. Can anybody please tell me how to give a query as part of the uri? Thank you in advance

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• SQL Server 2008 - Query takes forever to finish even though work is actually done

  - by Brian

  Running the following simple query in SSMS: UPDATE tblEntityAddress SET strPostCode= REPLACE(strPostCode,' ','') The update to the data (at least in memory) is complete in under a minute. I verified this by performing another query with transaction isolation level read uncommitted. The update query, however, continues to run for another 30 minutes. What is the issue here? Is this caused by a delay to write to disk? TIA

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• need help to construct query

  - by Learner

  i have the following result and i would like to construct the select query from the following result in java, Please help me how to go about , tablename columnname size order employee name 25 1 employee sex 25 2 employee contactNumber 50 3 employee salary 25 4 address street 25 5 address country 25 6 from this i would like to construct query like select T1.name, T1.sex,T1.contactNumber, T1.salaryT2.street, T2.contry from tablename1[employee] T1, tablename2[address] T2 how to construt the above query in java, here table name can be N also the columname can be also N. Please help me to achieve the above. Thanks and Regards

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• hadoop - large database query

  - by Mastergeek

  Situation: I have a Postgres DB that contains a table with several million rows and I'm trying to query all of those rows for a MapReduce job. From the research I've done on DBInputFormat, Hadoop might try and use the same query again for a new mapper and since these queries take a considerable amount of time I'd like to prevent this in one of two ways that I've thought up: 1) Limit the job to only run 1 mapper that queries the whole table and call it good. or 2) Somehow incorporate an offset in the query so that if Hadoop does try to use a new mapper it won't grab the same stuff. I feel like option (1) seems more promising, but I don't know if such a configuration is possible. Option(2) sounds nice in theory but I have no idea how I would keep track of the mappers being made and if it is at all possible to detect that and reconfigure. Help is appreciated and I'm namely looking for a way to pull all of the DB table data and not have several of the same query running because that would be a waste of time.

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• Strange LINQ to SQL Behavior

  - by mcass20

  What is wrong with the last query? Is it a bug or am I missing something? This query returns 2 records (correct): query = query.Where(Log => SqlMethods.Like(Log.FormattedMessage, "%<key>Name</key><value>David</value>%")); This query returns 2 records (correct): query = query.Where(Log => SqlMethods.Like(Log.FormattedMessage, "%<key>Name</key><value>%David%</value>%")); This query returns 0 records (correct): query = query.Where(Log => SqlMethods.Like(Log.FormattedMessage, "%<key>Name</key><value>av</value>%")); This query returns 2 records (correct): query = query.Where(Log => SqlMethods.Like(Log.FormattedMessage, "%<key>Name</key><value>%av%</value>%")); This query returns 0 records (correct): query = query.Where(Log => SqlMethods.Like(Log.FormattedMessage, "%<key>Name</key><value>v</value>%")); This query returns 15 records (incorrect, should return 2): query = query.Where(Log => SqlMethods.Like(Log.FormattedMessage, "%<key>Name</key><value>%v%</value>%"));

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• PHP | SQL syntax error when inserting array

  - by Philip

  Hi guys, I am having some trouble inserting an array into the sql database. my error is as follows: Unable to add : 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 '06:45:23,i want to leave a comment)' at line 1 My query var_dump is: string(136) "INSERT INTO news_comments (news_id,comment_by,comment_date,comment) VALUES (17263,Philip,2010-05-11 06:45:23,i want to leave a comment)" My question is how can i add an empty value to id as it is the primary key and not news_id my insert function looks like this: function insertQuery($tbl, &$data) { global $mysqli; $_SESSION['errors'] = array(); require_once '../config/mysqli.php'; $query = "INSERT INTO $tbl (".implode(',',array_keys($data)).") VALUES (".implode(',',array_values($data)).")"; var_dump($query); if($result = mysqli_query($mysqli, $query)) { //$id = mysqli_insert_id($mysqli); print 'Very well done sir!'; } else { array_push($_SESSION['errors'], 'Unable to add : ' . mysqli_error($mysqli)); } } Note: arrays are not my strong point so i may be using them in-correctly!

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• Why does this php/ajax query fail?

  - by Ashley Brown

  I'm ajaxing over to this php file. $a = 'old'; $b = 'new'; if ($_POST['info-type'] == $a || $b) { $info = $_POST['info-type']; $query = "SELECT * FROM `tld` WHERE type = '".$var."'"; } $query = "SELECT * FROM `tld` "; $result = mysqli_query($link,$query); while($row = mysqli_fetch_assoc($result)) { echo '<div>'.$row['something'].'</div>'; } The data posted is either 'all' 'new' or 'old'. If i send the data as either new or old, the script works and outputs as expected. If the posted data is neither new or old but all instead, it fails and don't show any errors or respond anything back. (I've monitored via dev tools aswell) So, I tried this if ($_POST['info-type'] == $a || $b) { $info = $_POST['info-type']; $var = "SELECT * FROM `tld` WHERE type = '".$var."'"; } elseif ($_POST['info-type'] == 'all'){ $query = "SELECT * FROM `tld` "; } But the script still fails. If i fully remove the IF statements and use the query without the WHERE clause like it is after the elseif, it works?

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• stepping into a linq query

  - by MyNameIsJob

  Is it possible to step into a linq query? I have a linq to entity framework 4 query in it's simplest form: List = List.Where(f => f.Value.ToString().ToLowerInvariant().Contains(filter.ToLowerInvariant())); It's a query against an Entity Framework DbContext and I'm having trouble seeing why it works for something like: List searching for 001 yields no results against the following list Test001 Test002 Test003 Test004 However any other search yields results (Such as t00 or Test) I was hoping to figure out a way to see the resulting sql but it appears that I need Intellitrace, which I don't currently have or possibly stepping through the query itself and see each iteration build itself.

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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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• Pessimistic locking is not working with Query API

  - by Reddy

  List esns=session.createQuery("from Pool e where e.status=:status "+ "order by uuid asc") .setString("status", "AVAILABLE") .setMaxResults(n) .setLockMode("e", LockMode.PESSIMISTIC_WRITE) .list(); I have the above query written, however it is not generating for update query and simultaneous updates are happening. I am using 3.5.2 version and it has a bug in Criteria API, is the same bug present in query API as well or I am doing something wrong?

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• GQL Query with __key__ in List of KEYs

  - by bossylobster

  In the GQL reference [1], it is encouraged to use the IN keyword with a list of values, and to construct a Key from hand the GQL query SELECT * FROM MyModel WHERE __key__ = KEY('MyModel', 'my_model_key') will succeed. However, using the code you would expect to work: SELECT * FROM MyModel WHERE __key__ IN (KEY('MyModel', 'my_model_key1'), KEY('MyModel', 'my_model_key2')) in the Datastore Viewer, there is a complaint of "Invalid GQL query string." What is the correct way to format such a query? [1] http://code.google.com/appengine/docs/python/datastore/gqlreference.html PS I know there are more efficient ways to do this in Python (without constructing a GQL query) and using the remote_api, but each call to the remote_api counts against quota. In an environment where quota is not (necessarily) free, quick and dirty queries are very helpful.

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