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  • Hash Join require Full Table Scan

    - by Pedro Magalhaes
    So, I want to know if to make a Hash Join between two tables is necessary to make a full table scan on the collumns? If i want to join COL1 wiht COL2, and COL1 is smaller, the It makes a full scan in COL1 creating a Hashmap then makes a full scan in COL2 using the sabe hash function. Is this correct?

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  • unhandled exception occured in c#

    - by abid
    hey. i`m getting this error that system.data.datarowview is not permitted in this contexxt. valid expressions are constants expressions and ( in some contexts). column name are not permitted.. can any body guide me what this error says.. can any one provide me a suggestion whether where im wrong.. any guesses guys??? im not getting it.. :/

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  • Porting Oracle Procedure to PostgreSQL

    - by Grasper
    I am porting an Oracle function into Postgres PGPLSQL.. I have been using this guide: http://www.postgresql.org/docs/8.1/static/plpgsql.html CREATE OR REPLACE PROCEDURE DATA_UPDATE (mission NUMBER, task NUMBER) AS BEGIN IF mission IS NOT NULL THEN UPDATE MISSION_OBJECTIVE MO SET (MO.MO_TKR_TOTAL_OFF_SCHEDULED, MO.MO_TKR_TOTAL_RECEIVERS) = (SELECT NVL(SUM(RR.TRQ_FUEL_OFFLOAD),0), NVL(SUM(RR.TRQ_NUMBER_RECEIVERS),0) FROM REFUELING_REQUEST RR, MISSION_REQUEST_PAIRING MRP WHERE MO.MSN_INT_ID = MRP.MSN_INT_ID AND MO.MO_INT_ID = MRP.MO_INT_ID AND MRP.REQ_INT_ID = RR.REQ_INT_ID) WHERE MO.MSN_INT_ID = mission AND MO.MO_INT_ID = task ; END IF ; COMMIT ; END ; I've got it this far: CREATE OR REPLACE FUNCTION DATA_UPDATE (NUMERIC, NUMERIC) RETURNS integer as ' DECLARE mission ALIAS for $1; task ALIAS for $2; BEGIN IF mission IS NOT NULL THEN UPDATE MISSION_OBJECTIVE MO SET (MO.MO_TKR_TOTAL_OFF_SCHEDULED, MO.MO_TKR_TOTAL_RECEIVERS) = (SELECT COALESCE(SUM(RR.TRQ_FUEL_OFFLOAD),0), COALESCE(SUM(RR.TRQ_NUMBER_RECEIVERS),0) FROM REFUELING_REQUEST RR, MISSION_REQUEST_PAIRING MRP WHERE MO.MSN_INT_ID = MRP.MSN_INT_ID AND MO.MO_INT_ID = MRP.MO_INT_ID AND MRP.REQ_INT_ID = RR.REQ_INT_ID) WHERE MO.MSN_INT_ID = mission AND MO.MO_INT_ID = task ; END IF; COMMIT; END; ' LANGUAGE plpgsql; This is the error I get: ERROR: syntax error at or near "SELECT" LINE 1: ...OTAL_OFF_SCHEDULED, MO.MO_TKR_TOTAL_RECEIVERS) = (SELECT COA... I do not know why this isn't working... any ideas?

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  • Best way to learn SQL Server

    - by Jason Baker
    So I'm getting a new job working with databases (Microsoft SQL Server to be precise). I know nothing about SQL much less SQL Server. They said they'd train me, but I want to take some initiative to learn about it on my own to be ahead. Where's the best place to start (tutorials, books, etc)? I want to learn more about the SQL language moreso than any of the fancy point and click stuff.

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  • what is the difference

    - by veilig
    I'm not even sure what this is called? But I'm trying to learn what the difference is between writing a function like this is in plpgsql: CREATE OR REPLACE FUNCTION foo() RETURNS TRIGGER AS $$ .... $$ LANGUAGE plpgsql; vs CREATE OR REPLACE FUNCTION foo() RETURNS TRIGGER AS $foo$ .... $foo$ LANGUAGE plpgsql; is there a difference when using $$ vs $foo$? why would someone choose one over another? perhaps I've just missed some documentation explaining the difference. If someone could enlighten me, I'd really appreciate it.

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  • Trapping errors in TClientDataSet.CommandText

    - by Rob McDonell
    I have a TClientDataSet connected to a TDataSetProvider, which in turn is connected to a TAdsTable. I set the SQL command and then open the ClientDataset something like this: try CDS.CommandText := 'SELECT * FROM tablename WHERE fieldname = 1'; CDS.Open except // trap exception here - this never gets executed! end; If the SQL statement in CommandText fails, however (syntax error or whatever) I get an exception within the Advantage code, but it never gets caught in my own exception handling code. Is there any way for me to trap this error and report it nicely to the user. Alternatively is there a way to verify the syntax of an SQL query before executing it? I'm using Delphi Pro 2009, and Advantage Local Server 9.

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  • SQL replicaton - collecting data

    - by Cicik
    Hi, I have master SQL server with DB Central and a lot of satellite SQL servers with DB Client. I need to collect data from log tables(LogTable) on Client(each client has own ID in log table) to one big table on Central(LogTableCentral). Data must go only from Client to Central On each Client I want to have only data for this Client I need solution with minimal amount of work on client side because of count of clients Central is MS SQL server Enterprise, Clients are MS SQL server 2005, 2008 Thanks a lot EDIT: data can be collected periodically(for example: every day at 01:00)

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  • Optimizing Oracle query

    - by Omnipresent
    SELECT MAX(verification_id) FROM VERIFICATION_TABLE WHERE head = 687422 AND mbr = 23102 AND RTRIM(LTRIM(lname)) = '.iq bzw' AND TO_CHAR(dob,'MM/DD/YYYY')= '08/10/2004' AND system_code = 'M'; This query is taking 153 seconds to run. there are millions of rows in VERIFICATION_TABLE. I think query is taking long because of the functions in where clause. However, I need to do ltrim rtrim on the columns and also date has to be matched in MM/DD/YYYY format. How can I optimize this query?

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  • Sorting NSSets of a core data entity - Objective-c

    - by ncohen
    Hi everyone, I would like to sort the data of a core data NSSet (I know we can do it only with arrays but let me explain...). I have an entity user who has a relationship to-many with the entity recipe. A recipe has the attributes name and id. I would like to get the data such that: Code: NSArray *id = [[user.recipes valueForKey:@"identity"] allObjects]; NSArray *name = [[user.recipes valueForKey:@"name"] allObjects]; if I take the object at index 1 in both arrays, they correspond to the same recipe... Thanks

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  • Getting hierarchy data from a self-referencing table

    - by Emanuil
    Let's say you have the following table: items(item_id, item_parent) ... and it is a self-referencing table as item_parent refers to item_id. What SQL query would you use to SELECT all items in the table along with their depth where the depth of an item is the sum of all parents and grand parents of that item. If the following is the content of the table: item_id item_parent ----------- ----------- 1 0 2 0 3 2 4 2 5 3 ... the query should retrieve the following set of objects: {"item_id":1,"depth":0} {"item_id":2,"depth":0} {"item_id":3,"depth":1} {"item_id":4,"depth":1} {"item_id":5,"depth":2} P.S. I'm looking for a MySQL supported approach.

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  • How do You Get a Specific Value From a System.Data.DataTable Object?

    - by Giffyguy
    I'm a low-level algorithm programmer, and databases are not really my thing - so this'll be a n00b question if ever there was one. I'm running a simple SELECT query through our development team's DAO. The DAO returns a System.Data.DataTable object containing the results of the query. This is all working fine so far. The problem I have run into now: I need to pull a value out of one of the fields of the first row in the resulting DataTable - and I have no idea where to even start. Microsoft is so confusing about this! Arrrg! Any advice would be appreciated. I'm not providing any code samples, because I believe that context is unnecessary here. I'm assuming that all DataTable objects work the same way, no matter how you run your queries - and therefore any additional information would just make this more confusing for everyone.

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  • PHP - static DB class vs DB singleton object

    - by Marco Demaio
    I don't want to create a discussion about singleton better than static or better than global, etc. I read dozens of questions about it on SO, but I couldn't come up with an answer to this SPECIFIC question, so I hope someone could now illuminate me buy answering this question with one (or more) real simple EXAMPLES, and not theoretical discussions. In my app I have the typical DB class needed to perform tasks on DB without having to write everywhere in code mysql_connect/mysql_select_db/mysql... (moreover in future I might decide to use another type of DB engine in place of mySQL so obviously I need a class of abstration). I could write the class either as a static class: class DB { private static $connection = FALSE; //connection to be opened //DB connection values private static $server = NULL; private static $usr = NULL; private static $psw = NULL; private static $name = NULL; public static function init($db_server, $db_usr, $db_psw, $db_name) { //simply stores connections values, withour opening connection } public static function query($query_string) { //performs query over alerady opened connection, if not open, it opens connection 1st } ... } or as a Singletonm class: class DBSingleton { private $inst = NULL; private $connection = FALSE; //connection to be opened //DB connection values private $server = NULL; private $usr = NULL; private $psw = NULL; private $name = NULL; public static function getInstance($db_server, $db_usr, $db_psw, $db_name) { //simply stores connections values, withour opening connection if($inst === NULL) $this->inst = new DBSingleton(); return $this->inst; } private __construct()... public function query($query_string) { //performs query over already opened connection, if connection is not open, it opens connection 1st } ... } Then after in my app if I wanto to query the DB i could do //Performing query using static DB object DB:init(HOST, USR, PSW, DB_NAME); DB::query("SELECT..."); //Performing query using DB singleton $temp = DBSingleton::getInstance(HOST, USR, PSW, DB_NAME); $temp->query("SELECT..."); My simple brain sees Singleton has got the only advantage to avoid declaring as 'static' each method of the class. I'm sure some of you could give me an EXAMPLE of real advantage of singleton in this specific case. Thanks in advance.

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  • e-shop implementation: Status for Orders?

    - by Guillermo
    Hello Again my fellow programmers out there, I'm designing and programming from scratch a online shop. It has a Module to manage "Orders" that are recieved via the frontend. I'm needing to have a status to know whats happening with an order in s certain moment, let's say the statuses are: Pending Payment Confirmed - Awaiting shipment Shipped Cancelled My question is a simple one, but is very important to decide on the store design, and is: What would you do so store this status: Would you create a column for it in the Orders table or would you just "calculate" the status of each order depending if payments has been recieved or shipments has been made for every order? (except I suppose for a is_cancelled column) What would be the best approach to model this kind of problem? PD: I even wish in the future to have these statuses configurable buy other clientes using the same software..

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  • Is it possible to calculate distance on GeoDjango in a SELECT statement?

    - by alex
    I am using MYSQL. I have a table with 1 column, a Point field. I want to SELECT all rows that have a point with a distance less than 50 meters of my given point. Simple enough, right? Below is how it's done in RAW SQL. But of course, I want to use GeoDjango to do this. cursor.execute("SELECT * FROM project_location WHERE\ (GLength(LineStringFromWKB(LineString(asbinary(utm), asbinary(PointFromWKB(point(%s, %s)))))) < 50)\

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  • Data store for capturing votes & aggregating them

    - by Nathan de Vries
    I'm interested in using Node.js as a socket server for stream-based communication with tens of thousands of clients. Clients will be sending votes for particular pieces of content, and receiving near-realtime updates of aggregated vote tallies from the server. The datastore needs to support: Storing the votes Summarising the votes in near-realtime Preventing multiple votes within an arbitrary time period (e.g. clients can only vote once for a piece of content every 1 minute) Something that already has client libraries for Node.js would be preferable.

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  • autoincrement in access sql is not working

    - by Thunder
    how can i create a table with autoincrement in access.Here is what i have been doing but not working. CREATE TABLE People_User_Master( Id INTEGER primary key AUTOINCREMENT , Name varchar(50) , LastName varchar(50) , Userid varchar(50) unique , Email varchar(50) , Phone varchar(50) , Pw varchar(50) , fk_Group int , Address varchar(150) )

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  • unhandeled exception occured in c#

    - by abid
    hey. i`m getting this error that system.data.datarowview is not permitted in this contexxt. valid expressions are constants expressions and ( in some contexts). column name are not permitted.. can any body guide me what this error says.. can any one provide me a suggestion whether where im wrong.. any guesses guys??? im not getting it.. :/

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  • Using Active Objects and BLOBs

    - by Andrew L.
    I am in a group of people who are creating a Defect Tracking program as a project. We have been using Active Objects and have run into some issues. Currently maximum file size for the blob is approx. 2Mb but we want to be able to increase it up to 2Gb. We currently have been looking at many sites and have not been able to find out how to increase the size. We are currently storing the blob as an array of bytes. Our current error says, Packet for Query is too large? We don't know how to set the variable, and we don't know how to set it using AO. We are programming this in Java, too. We are wondering if anyone has a solution to this problem. Thanks for the Help.

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  • Which MySQL Frontend shows foreign rows?

    - by Jeremy Rudd
    I once came across a MySQL Frontend app that displayed foreign linked rows within the parent row, if for instance the Events table has a foreign key to the Students table: Student ID Name DOB -- ---- --------- [+] 22 Bob 25-1-1984 [-] 21 Jane 25-1-1982 Event ID Student-ID Name Time -- ---------- ---- --------- 1 21 Event A 05:50 1 21 Event B 17:20 [+] 20 Jack 25-1-1980

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  • Can someone describe the nested set model from a C#/LINQ perspective?

    - by Chad
    I know the nested set model doesn't pertain to the C# language or LINQ directly... it's what I'm using to develop my web app. For hierarchical data (categories with sub-categories in my case), I'm currently using something similar to the Adjacency List model. At the moment, I've only got 2 levels of categories, but I'd like to take it further and allow for n levels of categories using the nested set model. I'm not quite clear on how to use it in a C# context. Here's the article I'm reading on the nested set model. Though this article cleared up my confusion some, I still have a big ?? in my head: - Is inserting, updating or deleting categories tedious? It looks like the left and right numbers would require re-numbering... what would the LINQ queries look like for the following scenarios? Delete a child node (re-number all node's left/right values) Delete a parent node (what do you do with the orphans?) Move a child node to a different parent node (renumber again) If my understanding is correct, at all times the child node's left/right values will always be between the parent node's left/right values, am I correct? Seems easy enough, if only the categories were static... most likely I need to spend more time to get my head around the concept. Any help is greatly appreciated!

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  • Is there a way to construct HTML/CSS in an HTML email such that if image X does not load, text Y will appear?

    - by wide_eyed_pupil
    I'm looking for something a little more sophisticated than the alt="Newsletter Heading text" attribute of <img> tag. So if the Masthead.png image doesn't load for whatever reason, I want the display text, say Font: 60px Helvetica Neue Black, Helvetica, ..., Sans Serif text-align: center to appear in the middle of the table cell that is my masthead instead of just the alt text in some small default font in top right corner. One idea I had was to use to put the image on-top of the text display but I don't know if z-depth is something I can use in email HTML(?4)?

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  • Algorithms for finding a numerical record in a list of ordered numbers

    - by Ankur
    I have a list of incomplete ordered numbers. I want to find a particular number with as few steps as possible. Are there any improvements on this algorithm, I assume you can count the set size without difficulty - it will be stored and updated every time a new item is added. Your object is to get your cursor over the value x The first number (smallest) is s, and the last number (greatest) is g. Take the midpoint m1 of the set: calculate is x < m1, If yes then s <= x < m1 If no then m1 < x <= g If m1 = x then you're done. Keep repeating till you find x. Basically dividing the set into two parts with each iteration till you hit x. The purpose is to retrieve a numerical id from a very large table to then find the associated other records. I would imagine this is the most trivial kind of indexing available, are there improvements?

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