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  • R equivalent of SELECT DISTINCT on two or more fields/variables

    - by wahalulu
    Say I have a dataframe df with two or more columns, is there an easy way to use unique() or other R function to create a subset of unique combinations of two or more columns? I know I can use sqldf() and write an easy "SELECT DISTINCT var1, var2, ... varN" query, but I am looking for an R way of doing this. It occurred to me to try ftable coerced to a dataframe and use the field names, but I also get the cross tabulations of combinations that don't exist in the dataset: uniques <- as.data.frame(ftable(df$var1, df$var2))

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  • MySQL One to Many order by number found in joined table

    - by Finbarr
    Two tables: table_a ------- table_a_id: (primary, int) table_b ------- table_a_id: (index, int, from table_a) table_b_value: (varchar) A one to many relationship between table_a_id and table_b_value. Given a query like this: SELECT DISTINCT(table_a_id) FROM table_a JOIN table_b ON table_a.table_a_id=table_b.table_a_id I want to order by the number of occurrences of table_a_id in table_b. I'm not really sure how to write this in MySQL.

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  • MySQL: how to index an "OR" clause

    - by JoséMi
    I'm executing the following query SELECT COUNT(*) FROM table WHERE field1='value' AND (field2 = 1000 OR field3 = 2000) There is one index over field1 and another composited over field2&field3. I see MySQL always selects the field1 index and then makes a join using the other two fields which is quite bad because it needs to join 146.000 rows. Suggestions on how to improve this? Thanks

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  • From Now() to Current_timestamp in Postgresql

    - by xRobot
    In mysql I am able to do this: SELECT * FROM table WHERE auth_user.lastactivity > NOW() - 100 now in postgresql I am using this query: SELECT * FROM table WHERE auth_user.lastactivity > CURRENT_TIMESTAMP - 100 but I get this error: operator does not exist: timestamp with time zone - integer How can I resolve ?

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  • Navigate through .Net Grid

    - by SH
    is there a way to navigate through gird found on this page by passing parameters in query string? http://pubrec3.hillsclerk.com/oncore/search.aspx?bd=01/01/2008&ed=12/31/2008&bt=O&lb=1000000&ub=1000000000&d=5/6/2010&pt=-1&dt=D,%20MTG&st=consideration Or any code suggestion? All example could i need in C#.

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  • How to test if a table is empty, using Hibernate

    - by landon9720
    Using Hibernate, what is the most efficient way to determine if a table is empty or non-empty? In other words, does the table have 0, or more than 0 rows? I could execute the HQL query select count(*) from tablename and then check if result is 0 or non-0, but this isn't optimal as I would be asking the database for more detail than I really need.

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  • What's the easiest way to create an extensible custom container in Flex?

    - by Chris R
    I want to create an MXML container component that has some of its own chrome -- a standard query display, et al -- and that supports the addition of child components to it. Something a lot like the existing mx:Panel class, which includes a title label, but acts like a plain mx:Box with regards to adding children. What's the easiest way to do this? Edit: To be clear, I want to be able to extend the container using MXML, so the "Multiple visual children" problem is relevant.

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  • 'Subquery returned more than 1 value' problem in EntityFramework

    - by plotnick
    I have one 'Transaction' entity object with 'Operations' navproperty with multiplicity of 'Many'. When I'm adding only one operation per transaction nothing happens, but when I'm trying to add more than one operation, db.SaveChanges() throws an exception like 'Subquery returned more than 1 value blah, blah, blah' How can I solve that? Help me guys please... BTW... Could you tell me how can I see the exact query string that EF passes to Sql Server on db.SaveChanges() method?

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  • WHERE condition accross multiple rows

    - by Chris G
    I have this table... -------------------------------------- | user_id | status | status_date | -------------------------------------- | 1 | Current | 2012-08-01 | | 1 | Referral | 2012-03-14 | | 2 | Referral | 2012-04-23 | | | | | -------------------------------------- How would I query to find a distinct user_id who has a referral date before 2012-06-30 AND either a current date of after 2012-06-30 or no current status record at all? Database is MySQL.

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  • When to use reflection to convert datarow to an object

    - by Daniel McNulty
    I'm in a situation now were I need to convert a datarow I've fetched from a query into a new instance of an object. I can do the obvious looping through columns and 'manually' assign these to properties of the object - or I can look into reflection such as this: http://www.codeproject.com/Articles/11914/Using-Reflection-to-convert-DataRows-to-objects-or What would I base the decision on? Just scalability??

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  • Insert or update when product is present using mysql

    - by Aryan
    main_product table productid outward shopid 333 2 44//present 343 4 44//present 353 5 44//present 363 1 44//present 373 2 44//not present min_product table productid outward shopid 333 1 44 343 1 44 353 1 44 363 1 44 SELECT DISTINCT (A.productid),A.outward, B.productid,B.outward FROM main_product A INNER JOIN min_product B on B.productid=A.product_id where A.shopid='44' and B.shopid='44' my question how can i INSERT OR UPDATE in one query using mysql by checking if it is present or not if present update else insert something like this? INSERT INTO mytable (key, value) VALUES ($newkey, $newvalue) ON DUPLICATE KEY UPDATE SET value = $newvalue

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  • Creating Auto Incrementing column in Google Appengine

    - by demos
    What is the easiest and most efficient way to create an auto-increment counter for every data row in google appengine? basically I want to give every row a unique row_number so that I can overcome the issue of only being able to get the first 1000 results in a select query. I can thus add a counter lies between condition and mine all the entires in the table.

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  • Php function within SQL statement syntax

    - by Vafello
    I have the following code. I would like username to take the value of the getUserName function however I am fighting with syntax. Can anybody tell me what should be the correct one? $query = "SELECT user FROM users_entity WHERE username = getUserName()";

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  • Copying an entire table with Postgres

    - by NudeCanalTroll
    Hello, I'm trying to copy the contents of one table into another in Postgres, however it appears some rows aren't being copied correctly: ActiveRecord::StatementInvalid: PGError: ERROR: column "email_date" is of type timestamp without time zone but expression is of type character varying HINT: You will need to rewrite or cast the expression. Is there any way I can have it automatically skip (or ignore) invalid rows? Here's the query I'm using: SET statement_timeout = 0; INSERT INTO emails3 SELECT * FROM emails

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  • MySQL select date, join statistic data - how?

    - by Webnet
    I have some statistics I need to report on a monthly basis. I need my query to return 0's for statistics which aren't there. The only way I know to do this is to use SQL to generate a list of days within the specified time period and LEFT JOIN the statistic data that I need to report on. Problem is.... I've never not selected from a table like that... how do I do that?

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  • Export CSV from Mysql

    - by ss888
    Hi, I'm having a bit of trouble exporting a csv file that is created from one of my mysql tables using php. The code I'm using prints the correct data, but I can't see how to download this data in a csv file, providing a download link to the created file. I thought the browser was supposed to automatically provide the file for download, but it doesn't. (Could it be because the below code is called using ajax?) Any help greatly appreciated - code below, S. include('../config/config.php'); //db connection settings $query = "SELECT * FROM isregistered"; $export = mysql_query ($query ) or die ( "Sql error : " . mysql_error( ) ); $fields = mysql_num_fields ( $export ); for ( $i = 0; $i < $fields; $i++ ) { $header .= mysql_field_name( $export , $i ) . "\t"; } while( $row = mysql_fetch_row( $export ) ) { $line = ''; foreach( $row as $value ) { if ( ( !isset( $value ) ) || ( $value == "" ) ) { $value = "\t"; } else { $value = str_replace( '"' , '""' , $value ); $value = '"' . $value . '"' . "\t"; } $line .= $value; } $data .= trim( $line ) . "\n"; } $data = str_replace( "\r" , "" , $data ); if ( $data == "" ) { $data = "\n(0) Records Found!\n"; } //header("Content-type: application/octet-stream"); //have tried all of these at sometime //header("Content-type: text/x-csv"); header("Content-type: text/csv"); //header("Content-type: application/csv"); header("Content-Disposition: attachment; filename=export.csv"); //header("Content-Disposition: attachment; filename=export.xls"); header("Pragma: no-cache"); header("Expires: 0"); echo '<a href="">Download Exported Data</a>'; //want my link to go in here... print "$header\n$data";

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  • MySQL Joining three tables

    - by text
    I am doing a query with three tables, the problem was one table has many occurrences of id of another. sample data: users: id answers: id:1 user_answer :1 id:1 user_answer :2 id:1 user_answer :3 Questions: id:1 answers :answer description id:2 answers :answer description id:3 answers :answer description How can I get all user information and all answer and its description, I used GROUP by user.id but it only returns only one answer. I want to return something like this list all of users answer: Name Q1 Q2 USERNAME ans1,ans2 ans1,ans2 comma separated description of answer here

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  • Problem with sql like

    - by phenevo
    Hi, I'm writing sql query to my SqlCommand, and some part of them looks like: WHERE Path like N'+(select top 1 path from [Paths] where objectcode=@objectCode and objecttype=@objectType)+%' order by path desc,objecttype desc I get no records , bu when I wrote the same in sql server 2005 i have plenty rows... where path like (select top 1 path from [Paths] where objectcode='eg' and objecttype='0')+'%' order by path desc What's wrong ?? @objectType is 'eg'

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