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  • Avoiding Nested Queries

    - by Midhat
    How Important is it to avoid nested queries. I have always learnt to avoid them like a plague. But they are the most natural thing to me. When I am designing a query, the first thing I write is a nested query. Then I convert it to joins, which sometimes takes a lot of time to get right. And rarely gives a big performance improvement (sometimes it does) So are they really so bad. Is there a way to use nested queries without temp tables and filesort

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  • How do I Put Several Select Statements into Different Columns

    - by Russ Bradberry
    I basically have 7 select statement that I need to have the results output into separate columns. Normally I would use a crosstab for this but I need a fast efficient way to go about this as there are over 7 billion rows in the table. I am using the vertica database system. Below is an example of my statements: SELECT COUNT(user_id) AS '1' FROM event_log_facts WHERE date_dim_id=20100101 SELECT COUNT(user_id) AS '2' FROM event_log_facts WHERE date_dim_id=20100102 SELECT COUNT(user_id) AS '3' FROM event_log_facts WHERE date_dim_id=20100103 SELECT COUNT(user_id) AS '4' FROM event_log_facts WHERE date_dim_id=20100104 SELECT COUNT(user_id) AS '5' FROM event_log_facts WHERE date_dim_id=20100105 SELECT COUNT(user_id) AS '6' FROM event_log_facts WHERE date_dim_id=20100106 SELECT COUNT(user_id) AS '7' FROM event_log_facts WHERE date_dim_id=20100107

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  • Algorithm for finding similar users through a join table

    - by Gdeglin
    I have an application where users can select a variety of interests from around 300 possible interests. Each selected interest is stored in a join table containing the columns user_id and interest_id. Typical users select around 50 interests out of the 300. I would like to build a system where users can find the top 20 users that have the most interests in common with them. Right now I am able to accomplish this using the following query: SELECT i2.user_id, count(i2.interest_id) AS count FROM interests_users as i1, interests_users as i2 WHERE i1.interest_id = i2.interest_id AND i1.user_id = 35 GROUP BY i2.user_id ORDER BY count DESC LIMIT 20; However, this query takes approximately 500 milliseconds to execute with 10,000 users and 500,000 rows in the join table. All indexes and database configuration settings have been tuned to the best of my ability. I have also tried avoiding the use of joins altogether using the following query: select user_id,count(interest_id) count from interests_users where interest_id in (13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,508) group by user_id order by count desc limit 20; But this one is even slower (~800 milliseconds). How could I best lower the time that I can gather this kind of data to below 100 milliseconds? I have considered putting this data into a graph database like Neo4j, but I am not sure if that is the easiest solution or if it would even be faster than what I am currently doing.

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  • How to select only the first rows for each unique value of a column

    - by nuit9
    Let's say I have a table of customer addresses: CName | AddressLine ------------------------------- John Smith | 123 Nowheresville Jane Doe | 456 Evergreen Terrace John Smith | 999 Somewhereelse Joe Bloggs | 1 Second Ave In the table, one customer like John Smith can have multiple addresses. I need the select query for this table to return only first row found where there are duplicates in 'CName'. For this table it should return all rows except the 3rd (or 1st - any of those two addresses are okay but only one can be returned). Is there a keyword I can add to the SELECT query to filter based on whether the server has already seen the column value before?

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  • Only the last run in a for loop in Javascript works

    - by Mengfei Murphy
    Here is a for loop written by Javascript. It is trying to apply queries for websql. for (var i = 0; i < 10; i++){ db.transaction(function (tx){ tx.executeSql('INSERT INTO ProjSetsT (ProjID) VALUES (?);', [i]); }); } The attempt is obvious, I tried to add values "0, 1, 2, ... 9" into column ProjID in table ProjSetsT. It does not work. I only got the last element, i.e. "9" inserted, but not the first eight numbers. Is there any syntax mistakes?

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  • file handling in .net

    - by Indranil Mutsuddy
    I have developed an application in vb.net2008 and database sqlserver. Now i want to ignore the database (it has 1 table as customer(name,password,hour,minute)) as i dont want my client to install sqlserver separately or other overheads. I am planning to do the whole using file handling in vb.net(manipulating the data in files itself eg change username, password etc). As I am new i don't actually know the proper way and of course need assistance.

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  • Maximum of averages

    - by Qtacz
    I'm supposed to get every departments average wage and only show the department with the highest average wage. I figured out this query, but it doesn't work. Anyone got some ideas? SELECT department, max(avg(wage)) FROM employees GROUP BY department; I get this error: ERROR at line 1: ORA-00937: not a single-group group function

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  • Building Stored Procedure to group data into ranges with roughly equal results in each bucket

    - by Len
    I am trying to build one procedure to take a large amount of data and create 5 range buckets to display the data. the buckets ranges will have to be set according to the results. Here is my existing SP GO /****** Object: StoredProcedure [dbo].[sp_GetRangeCounts] Script Date: 03/28/2010 19:50:45 ******/ SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO ALTER PROCEDURE [dbo].[sp_GetRangeCounts] @idMenu int AS declare @myMin decimal(19,2), @myMax decimal(19,2), @myDif decimal(19,2), @range1 decimal(19,2), @range2 decimal(19,2), @range3 decimal(19,2), @range4 decimal(19,2), @range5 decimal(19,2), @range6 decimal(19,2) SELECT @myMin=Min(modelpropvalue), @myMax=Max(modelpropvalue) FROM xmodelpropertyvalues where modelPropUnitDescriptionID=@idMenu set @myDif=(@myMax-@myMin)/5 set @range1=@myMin set @range2=@myMin+@myDif set @range3=@range2+@myDif set @range4=@range3+@myDif set @range5=@range4+@myDif set @range6=@range5+@myDif select @myMin,@myMax,@myDif,@range1,@range2,@range3,@range4,@range5,@range6 select t.range as myRange, count(*) as myCount from ( select case when modelpropvalue between @range1 and @range2 then 'range1' when modelpropvalue between @range2 and @range3 then 'range2' when modelpropvalue between @range3 and @range4 then 'range3' when modelpropvalue between @range4 and @range5 then 'range4' when modelpropvalue between @range5 and @range6 then 'range5' end as range from xmodelpropertyvalues where modelpropunitDescriptionID=@idmenu) t group by t.range order by t.range This calculates the min and max value from my table, works out the difference between the two and creates 5 buckets. The problem is that if there are a small amount of very high (or very low) values then the buckets will appear very distorted - as in these results... range1 2806 range2 296 range3 75 range5 1 Basically I want to rebuild the SP so it creates buckets with equal amounts of results in each. I have played around with some of the following approaches without quite nailing it... SELECT modelpropvalue, NTILE(5) OVER (ORDER BY modelpropvalue) FROM xmodelpropertyvalues - this creates a new column with either 1,2,3,4 or 5 in it ROW_NUMBER()OVER (ORDER BY modelpropvalue) between @range1 and @range2 ROW_NUMBER()OVER (ORDER BY modelpropvalue) between @range2 and @range3 or maybe i could allocate every record a row number then divide into ranges from this?

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  • Ordering Wordpress posts by most recently commented on

    - by Hardseat
    What's the query to list wordpress posts by most recent, with posts most recently commented on going to the top of the order? (Standard "message board" style) This post looked promising: http://stackoverflow.com/questions/698438/ordering-wordpress-posts-by-most-recent-comment But the query is clearly wrong. Can anyone help?

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  • Can't get Sum() working in Northwind example

    - by Vince
    Hi, The following code is generating a runtime error and I have no idea why. from o in Orders group o by o.Employee into employeeOrders select new { employeeOrders.Key.EmployeeID, employeeOrders.Key.FirstName, Orders = from eord in employeeOrders orderby eord.OrderID select new { eord.OrderID, eord.OrderDate, OrderTotal=eord.OrderDetails.Sum (od => od.UnitPrice) } } The error is Member access 'System.Decimal UnitPrice' of 'LINQPad.User.OrderDetails' not legal on type 'LINQPad.User.Orders I've also tried this in VS2010 with a standard drag and drop data context and same thing. Thanks in advance

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  • Insert multiple records from a XML string differing on one parameter in SQL SERVER 2008

    - by Rohit
    Below in a query which inserts records to SimpleDictationProfileMapping table after reading it from a XML string. Now this query inserts a single record in which DictationCaptureProfileID is @dictationCaptureProfileId . Now i want to insert multiple rows in which @dictationCaptureProfileId is different and other 2 values are same. What i want to achieve by this is in case parent changes all child values should also change. INSERT INTO SimpleDictationProfileMapping ( DictationCaptureProfileID, DictationProfileMappingAttributeID, DictationProfileMappingAttributeValue ) SELECT @dictationCaptureProfileId, row.value('@attrId','varchar(max)'), row.value('@value', 'varchar(max)') FROM @simpleDictationCaptureProfileMappings.nodes('/simpleMappingAtribute/attribute') AS d ( row ) ; I want INSERT INTO SimpleDictationProfileMapping ( DictationCaptureProfileID OR (SELECT DictationCaptureProfileID FROM DictationCaptureProfile WHERE SystemDictationCaptureProfileID = @systemDictationCaptureProfileID), DictationProfileMappingAttributeID, DictationProfileMappingAttributeValue ) SELECT @dictationCaptureProfileId , row.value('@attrId','varchar(max)'), row.value('@value', 'varchar(max)') FROM @simpleDictationCaptureProfileMappings.nodes ('/simpleMappingAtribute/attribute') AS d ( row ) ; Please tell how to achieve this.

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  • Speeding up PostgreSQL query where data is between two dates

    - by Roger
    I have a large table ( 50m rows) which has some data with an ID and timestamp. I need to query the table to select all rows with a certain ID where the timestamp is between two dates, but it currently takes over 2 minutes on a high end machine. I'd really like to speed it up. I have found this tip which recommends using a spatial index, but the example it gives is for IP addresses. However, the speed increase (436s to 3s) is impressive. How can I use this with timestamps?

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  • Select proper columns from JOIN statement

    - by Alexander Stalt
    I have two tables: table1, table2. Table1 has 10 columns, table2 has 2 columns. SELECT * FROM table1 AS T1 INNER JOIN table2 AS T2 ON T1.ID = T2.ID I want to select all columns from table1 and only 1 column from table2. Is it possible to do that without enumerating all columns from table1 ?

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  • Using CASE Statements in LEFT OUTER JOIN in SQL

    - by s khan
    I've got a scenario where I want to switch on two different tables in an outer join. It goes something like this:- select mytable.id, yourtable.id from mytable left outer join (case when mytable.id = 2 then table2 yourtable on table1.id = table2.id else table3 yourtable on table1.id = table3.id end) ...but it doesn't work. Any suggestions?

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  • Loading Fact Table + Lookup / UnionAll for SK lookups.

    - by Nev_Rahd
    I got to populate FactTable with 12 lookups to dimension table to get SK's, of which 6 are to different Dim Tables and rest 6 are lookup to same DimTable (type II) doing lookup to same natural key. Ex: PrimeObjectID = lookup to DimObject.ObjectID = get ObjectSK and got other columns which does same OtherObjectID1 = lookup to DimObject.ObjectID = get ObjectSK OtherObjectID2 = lookup to DimObject.ObjectID = get ObjectSK OtherObjectID3 = lookup to DimObject.ObjectID = get ObjectSK OtherObjectID4 = lookup to DimObject.ObjectID = get ObjectSK OtherObjectID5 = lookup to DimObject.ObjectID = get ObjectSK for such multiple lookup how should go in my SSIS package. for now am using lookup / unionall foreach lookup. Is there a better way to this.

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  • How can I make a multi search SPROC/UDF by passing a tabled-value to it?

    - by Shimmy
    I actually want to achieve the following description This is the table argument I want to pass to the server <items> <item category="cats">1</item> <item category="dogs">2</item> </items> SELECT * FROM Item WHERE Item.Category = <one of the items in the XML list> AND Item.ReferenceId = <the corresponding value of that item xml element> --Or in other words: SELECT FROM Items WHERE Item IN XML according to the splecified columns. Am I clear enought? I don't mind to do it in a different way other than xml. What I need is selecting values that mach an array of two of its columns' values.

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  • Why does this MySQL function return null?

    - by Shore
    Description: the query actually run have 4 results returned,as can be see from below, what I did is just concate the items then return, but unexpectedly,it's null. I think the code is self-explanatory: DELIMITER | DROP FUNCTION IF EXISTS get_idiscussion_ask| CREATE FUNCTION get_idiscussion_ask(iask_id INT UNSIGNED) RETURNS TEXT DETERMINISTIC BEGIN DECLARE done INT DEFAULT 0; DECLARE body varchar(600); DECLARE created DATETIME; DECLARE anonymous TINYINT(1); DECLARE screen_name varchar(64); DECLARE result TEXT; DECLARE cur1 CURSOR FOR SELECT body,created,anonymous,screen_name from idiscussion left join users on idiscussion.uid=users.id where idiscussion.iask_id=iask_id; DECLARE CONTINUE HANDLER FOR SQLSTATE '02000' SET done = 1; SET result = ''; OPEN cur1; REPEAT FETCH cur1 INTO body, created, anonymous, screen_name; SET result = CONCAT(result,'<comment><body><![CDATA[',body,']]></body>','<replier>',if(screen_name is not null and !anonymous,screen_name,''),'</replier>','<created>',created,'</created></comment>'); UNTIL done END REPEAT; CLOSE cur1; RETURN result; END | DELIMITER ; mysql> DELIMITER ; mysql> select get_idiscussion_ask(1); +------------------------+ | get_idiscussion_ask(1) | +------------------------+ | NULL | +------------------------+ 1 row in set (0.01 sec) mysql> SELECT body,created,anonymous,screen_name from idiscussion left join users on idiscussion.uid=users.id where idiscussion.iask_id=1; +------+---------------------+-----------+-------------+ | body | created | anonymous | screen_name | +------+---------------------+-----------+-------------+ | haha | 2009-05-27 04:57:51 | 0 | NULL | | haha | 2009-05-27 04:57:52 | 0 | NULL | | haha | 2009-05-27 04:57:52 | 0 | NULL | | haha | 2009-05-27 04:57:53 | 0 | NULL | +------+---------------------+-----------+-------------+ 4 rows in set (0.00 sec) For those who don't think the code is self-explanatory: Why the function returns NULL?

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  • Creating a [materialised]view from generic data in Oracle/Mysql

    - by Andrew White
    I have a generic datamodel with 3 tables CREATE TABLE Properties ( propertyId int(11) NOT NULL AUTO_INCREMENT, name varchar(80) NOT NULL ) CREATE TABLE Customers ( customerId int(11) NOT NULL AUTO_INCREMENT, customerName varchar(80) NOT NULL ) CREATE TABLE PropertyValues ( propertyId int(11) NOT NULL, customerId int(11) NOT NULL, value varchar(80) NOT NULL ) INSERT INTO Properties VALUES (1, 'Age'); INSERT INTO Properties VALUES (2, 'Weight'); INSERT INTO Customers VALUES (1, 'Bob'); INSERT INTO Customers VALUES (2, 'Tom'); INSERT INTO PropertyValues VALUES (1, 1, '34'); INSERT INTO PropertyValues VALUES (2, 1, '80KG'); INSERT INTO PropertyValues VALUES (1, 2, '24'); INSERT INTO PropertyValues VALUES (2, 2, '53KG'); What I would like to do is create a view that has as columns all the ROWS in Properties and has as rows the entries in Customers. The column values are populated from PropertyValues. e.g. customerId Age Weight 1 34 80KG 2 24 53KG I'm thinking I need a stored procedure to do this and perhaps a materialised view (the entries in the table "Properties" change rarely). Any tips?

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  • Pick Return Values of Stored Procedure

    - by Juergen
    Hi, I have a stored procedure that returns a result with 250!!! columns. But I only need 3 out of the 250. I want to call the SP and put only the 3 column values in a temp table. I don't want to define a temp table with 250 columns! This is how I would like to do it, but this doesn't work of course: create #myTempTable (id int, value1 int, value2 int) insert into #myTempTable exec myBigFatStoredProc Can it be done anyhow? Bye Juergen

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  • Cassandra Production ready on Windows?

    - by BlackTea
    Question anyone know of any success stories of Cassandra running on windows in a production environment? I'm doing some work on Cassandra and trying to find the correct platform for it currently the platform is windows running MS-SQLas the data store. what are the dis-advantages if any when running Cassandra on a windows environment.

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