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  • How to join table to itself and select max values in SQL

    - by Jakub Konop
    I have a contracts table: contractId date price partId 1 20120121 10 1 2 20110130 9 1 3 20130101 15 2 4 20110101 20 2 The contract with greatest date being the active contract (don't blame me, I blame infor for creating xpps) I need to create query to see only active contracts (one contract per part, the contract with highest date). So the result of the query should be like this: contractId date price partId 1 20120121 10 1 3 20130101 15 2 I am out of ideas here, I tried self joining the table, I tried aggregation functions, but I can't figure it out. If anyone would have any idea, please share them with me..

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  • Speed of QHash lookups using QStrings as keys.

    - by Ryan R.
    I need to draw a dynamic overlay on a QImage. The component parts of the overlay are defined in XML and parsed out to a QHash<QString, QPicture> where the QString is the name (such as "crosshairs") and the QPicture is the resolution independent drawing. I then draw components of the overlay as they are needed at a position determined during runtime. Example: I have 10 pictures in my QHash composing every possible element in a HUD. During a particular frame of video I need to draw 6 of them at different positions on the image. During the next frame something has changed and now I only need to draw 4 of them but 2 of those positions have changed. Now to my question: If I am trying to do this quickly, should I redefine my QHash as QHash<int, QPicture> and enumerate the keys to counteract the overhead caused by string comparisons; or are the comparisons not going to make a very big impact on performance? I can easily make the conversion to integer keys as the XML parser and overlay composer are completely separate classes; but I would like to use a consistent data structure across the application. Should I overcome my desire for consistency and re-usability in order to increase performance? Will it even matter very much if I do?

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  • Problems writing a query to join two tables

    - by Psyche
    Hello, I'm working on a script which purpose is to grant site users access to different sections of the site menu. For this I have created two tables, "menu" and "rights": menu - id - section_name rights - id - menu_id (references column id from menu table) - user_id (references column id from users table) How can a query be written in order to get all menu sections and mark the ones where a given user has access. I'm using PHP and Postgres. Thank you.

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  • MySQL query puzzle - finding what WOULD have been the most recent date

    - by Hank
    I've looked all over and haven't yet found an intelligent way to handle this, though I feel sure one is possible: One table of historical data has quarterly information: CREATE TABLE Quarterly ( unique_ID INT UNSIGNED NOT NULL, date_posted DATE NOT NULL, datasource TINYINT UNSIGNED NOT NULL, data FLOAT NOT NULL, PRIMARY KEY (unique_ID)); Another table of historical data (which is very large) contains daily information: CREATE TABLE Daily ( unique_ID INT UNSIGNED NOT NULL, date_posted DATE NOT NULL, datasource TINYINT UNSIGNED NOT NULL, data FLOAT NOT NULL, qtr_ID INT UNSIGNED, PRIMARY KEY (unique_ID)); The qtr_ID field is not part of the feed of daily data that populated the database - instead, I need to retroactively populate the qtr_ID field in the Daily table with the Quarterly.unique_ID row ID, using what would have been the most recent quarterly data on that Daily.date_posted for that data source. For example, if the quarterly data is 101 2009-03-31 1 4.5 102 2009-06-30 1 4.4 103 2009-03-31 2 7.6 104 2009-06-30 2 7.7 105 2009-09-30 1 4.7 and the daily data is 1001 2009-07-14 1 3.5 ?? 1002 2009-07-15 1 3.4 && 1003 2009-07-14 2 2.3 ^^ then we would want the ?? qtr_ID field to be assigned '102' as the most recent quarter for that data source on that date, and && would also be '102', and ^^ would be '104'. The challenges include that both tables (particularly the daily table) are actually very large, they can't be normalized to get rid of the repetitive dates or otherwise optimized, and for certain daily entries there is no preceding quarterly entry. I have tried a variety of joins, using datediff (where the challenge is finding the minimum value of datediff greater than zero), and other attempts but nothing is working for me - usually my syntax is breaking somewhere. Any ideas welcome - I'll execute any basic ideas or concepts and report back.

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  • Using a join with three tables when a field might be null

    - by John
    Hello, The code below works great. It combines data from two MySQL tables. I would like to modify it by pulling in some data from a third MySQL table called "comment." In the HTML table below, "title" is a field in the MySQL table "submission." Every "title" has a corresponding "submissionid" field. The field "submissionid" is also found in the "comment" MySQL table. In the HTML table below, I would like "countComments" to equal the number of times a field called "commentid" appears in the MySQL table "comment" for any given "submissionid," where the "submissionid" is the same in both the "submission" and "comment" tables, and where the "submissionid" corresponds to the "title" being used. Here's the catch: if there is no row in the MySQL table "comment" that corresponds with the "submissionid" being used for "table", I would like "countComments" to equal to zero. How can I do this? Thanks in advance, John $sqlStr = "SELECT s.loginid, s.title, s.url, s.displayurl, l.username FROM submission AS s, login AS l WHERE s.loginid = l.loginid ORDER BY s.datesubmitted DESC LIMIT 10"; $result = mysql_query($sqlStr); $arr = array(); echo "<table class=\"samplesrec\">"; while ($row = mysql_fetch_array($result)) { echo '<tr>'; echo '<td class="sitename1"><a href="http://www.'.$row["url"].'">'.$row["title"].'</a></td>'; echo '</tr>'; echo '<tr>'; echo '<td class="sitename2"><a href="http://www...com/sandbox/members/index.php?profile='.$row["username"].'">'.$row["username"].'</a><a href="http://www...com/sandbox/comments/index.php?submission='.$row["title"].'">'.$row["countComments"].'</a></td>'; echo '</tr>'; } echo "</table>";

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  • Ruby/Rails - Add records to an object with each loop iteration / Object vs Arrays

    - by ChrisWesAllen
    I'm trying to figure out how to add records to an existing object for each iteration of a loop. I'm having a hard time discovering the difference between an object and an array. I have this @events = Event.find(1) @loops = Choices.find(:all, :limit => 5) #so loop for 5 instances of choice model for loop in @loops @events = Event.find(:all,:conditions => ["event.id = ?", loop.event_id ]) end I'm trying to add a new events to the existing @events object based on the id of whatever the loop variable is. But the ( = ) operator just creates a new instance of the @events object. I tried ( += ) and ( << ) as operators but got the error "You have a nil object when you didn't expect it! You might have expected an instance of Array. The error occurred while evaluating nil" I tried created an array events = [] events << Event.find(1) @loops = Choices.find(:all, :limit => 5) #so loop for 5 instances of choice model for loop in @loops events << Event.find(:all,:conditions => ["event.id = ?", loop.event_id ]) end But I dont know how to call that arrays attributes within the view With objects I was able do create a loop within the view and call all the attributes of that object as well... <table> <% for event in @events %> <tr> <td><%= link_to event.title, event %></td> <td><%= event.start_date %></td> <td><%= event.price %></td> </tr> <% end %> </table> How could i do this with an array set? So the questions are 1) Whats the difference between arrays and objects? 2) Is there a way to add into the existing object for each iteration? 3) If I use an array, is there a way to call the attributes for each array record within the view?

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  • Efficient algorithm to distribute work?

    - by Zwei Steinen
    It's a bit complicated to explain but here we go. We have problems like this (code is pseudo-code, and is only for illustrating the problem. Sorry it's in java. If you don't understand, I'd be glad to explain.). class Problem { final Set<Integer> allSectionIds = { 1,2,4,6,7,8,10 }; final Data data = //Some data } And a subproblem is: class SubProblem { final Set<Integer> targetedSectionIds; final Data data; SubProblem(Set<Integer> targetedSectionsIds, Data data){ this.targetedSectionIds = targetedSectionIds; this.data = data; } } Work will look like this, then. class Work implements Runnable { final Set<Section> subSections; final Data data; final Result result; Work(Set<Section> subSections, Data data) { this.sections = SubSections; this.data = data; } @Override public void run(){ for(Section section : subSections){ result.addUp(compute(data, section)); } } } Now we have instances of 'Worker', that have their own state sections I have. class Worker implements ExecutorService { final Map<Integer,Section> sectionsIHave; { sectionsIHave = {1:section1, 5:section5, 8:section8 }; } final ExecutorService executor = //some executor. @Override public void execute(SubProblem problem){ Set<Section> sectionsNeeded = fetchSections(problem.targetedSectionIds); super.execute(new Work(sectionsNeeded, problem.data); } } phew. So, we have a lot of Problems and Workers are constantly asking for more SubProblems. My task is to break up Problems into SubProblem and give it to them. The difficulty is however, that I have to later collect all the results for the SubProblems and merge (reduce) them into a Result for the whole Problem. This is however, costly, so I want to give the workers "chunks" that are as big as possible (has as many targetedSections as possible). It doesn't have to be perfect (mathematically as efficient as possible or something). I mean, I guess that it is impossible to have a perfect solution, because you can't predict how long each computation will take, etc.. But is there a good heuristic solution for this? Or maybe some resources I can read up before I go into designing? Any advice is highly appreciated!

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  • Bulk update + SQL + self join

    - by Nev_Rahd
    Hello All I would like to update a column in Table with reference to other column(s) in same table. Ex: As in figure below - I would like to update effective endate with min date whichever is greater than effective Start Date of currrent record. How can this be acheived in T-SQL. Can this be done with single update statement ? Thanks.

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  • How do I call a function name that is stored in a hash in Perl?

    - by Ether
    I'm sure this is covered in the documentation somewhere but I have been unable to find it... I'm looking for the syntactic sugar that will make it possible to call a method on a class whose name is stored in a hash (as opposed to a simple scalar): use strict; use warnings; package Foo; sub foo { print "in foo()\n" } package main; my %hash = (func => 'foo'); Foo->$hash{func}; If I copy $hash{func} into a scalar variable first, then I can call Foo->$func just fine... but what is missing to enable Foo->$hash{func} to work? (EDIT: I don't mean to do anything special by calling a method on class Foo -- this could just as easily be a blessed object (and in my actual code it is); it was just easier to write up a self-contained example using a class method.) EDIT 2: Just for completeness re the comments below, this is what I'm actually doing (this is in a library of Moose attribute sugar, created with Moose::Exporter): # adds an accessor to a sibling module sub foreignTable { my ($meta, $table, %args) = @_; my $class = 'MyApp::Dir1::Dir2::' . $table; my $dbAccessor = lcfirst $table; eval "require $class" or do { die "Can't load $class: $@" }; $meta->add_attribute( $table, is => 'ro', isa => $class, init_arg => undef, # don't allow in constructor lazy => 1, predicate => 'has_' . $table, default => sub { my $this = shift; $this->debug("in builder for $class"); ### here's the line that uses a hash value as the method name my @args = ($args{primaryKey} => $this->${\$args{primaryKey}}); push @args, ( _dbObject => $this->_dbObject->$dbAccessor ) if $args{fkRelationshipExists}; $this->debug("passing these values to $class -> new: @args"); $class->new(@args); }, ); } I've replaced the marked line above with this: my $pk_accessor = $this->meta->find_attribute_by_name($args{primaryKey})->get_read_method_ref; my @args = ($args{primaryKey} => $this->$pk_accessor); PS. I've just noticed that this same technique (using the Moose meta class to look up the coderef rather than assuming its naming convention) cannot also be used for predicates, as Class::MOP::Attribute does not have a similar get_predicate_method_ref accessor. :(

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  • How to do a join with ttwo tables ??

    - by bahamut100
    HI, I try to translate this query : SELECT * FROM `reunion` , lieu WHERE reunion.lieu_reunion = lieu.id_lieu to propel query : $c=new Criteria(); $c->addJoin(ReunionPeer::LIEU_REUNION,LieuPeer::ID_LIEU, Criteria::LEFT_JOIN); $this->reunions = ReunionPeer::doSelect($c); But in my template, when I made a print_r($reunions), the field "ville" (from the table 'lieu') is not present. Why ??

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  • Linq2Sql How to write outer join query?

    - by Malcolm
    Hi, I have following SQL tables. ImportantMessages impID Message ImportantMessageUsers imuID imuUserID imuImpID I want to write a Linq2Sql query so that it returns any rows from ImportantMessages that does not have a record in ImportantMessagesUsers. Matchiing fields are impID ----- imuImpID Assume imuUserID of 6

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  • Combining Java hashcodes into a "master" hashcode

    - by Nick Wiggill
    I have a vector class with hashCode() implemented. It wasn't written by me, but uses 2 prime numbers by which to multiply the 2 vector components before XORing them. Here it is: /*class Vector2f*/ ... public int hashCode() { return 997 * ((int)x) ^ 991 * ((int)y); //large primes! } ...As this is from an established Java library, I know that it works just fine. Then I have a Boundary class, which holds 2 vectors, "start" and "end" (representing the endpoints of a line). The values of these 2 vectors are what characterize the boundary. /*class Boundary*/ ... public int hashCode() { return 1013 * (start.hashCode()) ^ 1009 * (end.hashCode()); } Here I have attempted to create a good hashCode() for the unique 2-tuple of vectors (start & end) constituting this boundary. My question: Is this hashCode() implementation going to work? (Note that I have used 2 different prime numbers in the latter hashCode() implementation; I don't know if this is necessary but better to be safe than sorry when trying to avoid common factors, I guess -- since I presume this is why primes are popular for hashing functions.)

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  • SQL Query over three different tables

    - by choise
    i got three tables CATS id name ------------------------------ 1 category1 2 category2 3 category3 4 category4 PRODUCT id name ------------------------------ 1 product1 2 product2 ZW-CAT-PRODUCT id_cats id_product ------------------------------ 1 1 3 1 4 2 now i want to get my products and their categories product1 => category1,category3 product2 => category4 is there a way to get this array (or object or something) with one mysql query? i tried a bit with JOINS, but it seems thats this is not exactly what i need, or? currently i'm using 3 querys (i think thats too much). any suggestions?

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  • Fetch Max from a date column grouped by a particular field

    - by vamyip
    Hi, I have a table similar to this: LogId RefId Entered ================================== 1 1 2010-12-01 2 1 2010-12-04 3 2 2010-12-01 4 2 2010-12-06 5 3 2010-12-01 6 1 2010-12-10 7 3 2010-12-05 8 4 2010-12-01 Here, LogId is unique; For each RefId, there are multiple entries with timestamp. What I want to extract is LogId for each latest RefId. I tried solutions from this link:http://stackoverflow.com/questions/121387/sql-fetch-the-row-which-has-the-max-value-for-a-column. But, it returns multiple rows with same RefId. Can someone help me with this? Thanks Vamyip

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  • mysql - combining columns and tables

    - by Phil Jackson
    Hi, I'm not much of a SQL man so I'm seeking help for this one. I have a site where I have a database for all accounts and whatnot, and another for storing actions that the user has done on the site. Each user has their own table but I want to combine the data of each user group ( all users that are "linked together" ) and order that data in the time the actions took place. Heres what I have; <?php $query = "SELECT `TALKING_TO` FROM `nnn_instant_messaging` WHERE `AUTHOR` = '" . DISPLAY_NAME . "' AND `TALKING_TO` != ''"; $query = mysql_query( $query, $CON ) or die( "_error_ " . mysql_error()); if( mysql_num_rows( $query ) != 0 ) { $table_str = ""; $select_ref_clause = "( "; $select_time_stamp_clause = "( "; while( $row = mysql_fetch_array( $query ) ) { $table_str .= "`actvbiz_networks`.`" . $row['TALKING_TO'] . "`, "; $select_ref_clause .= "`actvbiz_networks`.`" . $row['TALKING_TO'] . ".REF`, "; $select_time_stamp_clause .= "`actvbiz_networks`.`" . $row['TALKING_TO'] . ".TIME_STAMP`, "; } $table_str = $table_str . "`actvbiz_networks`.`" . DISPLAY_NAME . "`"; $select_ref_clause = substr($select_ref_clause, 0, -2) . ") AS `REF`, "; $select_time_stamp_clause = substr($select_time_stamp_clause, 0, -2) . " ) AS `TIME_STAMP`"; }else{ $table_str = "`actvbiz_networks`.`" . DISPLAY_NAME . "`"; $select_ref_clause = "`REF`, "; $select_time_stamp_clause = "`TIME_STAMP`"; } $where_clause = $select_ref_clause . $select_time_stamp_clause; $query = "SELECT " . $where_clause . " FROM " . $table_str . " ORDER BY TIME_STAMP"; die($query); $query = mysql_query( $query, $CON ) or die( "_error_ " . mysql_error()); if( mysql_num_rows( $query ) != 0 ) { }else{ ?> <p>Currently no actions have taken place in your network.</p> <?php } ?> The code above returns the sql statement: SELECT ( `actvbiz_networks`.`john_doe.REF`, `actvbiz_networks`.`Emmalene_Jackson.REF`) AS `REF`, ( `actvbiz_networks`.`john_doe.TIME_STAMP`, `actvbiz_networks`.`Emmalene_Jackson.TIME_STAMP` ) AS `TIME_STAMP` FROM `actvbiz_networks`.`john_doe`, `actvbiz_networks`.`Emmalene_Jackson`, `actvbiz_networks`.`act_web_designs` ORDER BY TIME_STAMP I really am learning on my feet with SQL. Its not the PHP I have a problem with ( I can quite happly code away with PHP ) I'ts just help with the SQL statement. Any help much appreciated, REgards, Phil

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  • Oracle (Old?) Joins - A tool for conversion?

    - by Grasper
    I have been porting oracle selects, and I have been running across a lot of queries like so: SELECT e.last_name, d.department_name FROM employees e, departments d WHERE e.department_id(+) = d.department_id; ...and: SELECT last_name, d.department_id FROM employees e, departments d WHERE e.department_id = d.department_id(+); Are there any guides/tutorials for converting all of the variants of the (+) syntax? What is that syntax even called (so I can scour google)? Even better.. Is there a tool that will do this conversion for me? When was this standard phased out? Any info is appreciated.

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  • Best way to map/join two autogenerated enums

    - by tomlip
    What is the best C++ (not C++11) way of joining two enums from autogenerated class similar to one presented below: namespace A { namespace B { ... class CarInfo { enum State { // basically same enums defined in different classes Running, Stopped, Broken } } class BikeInfo { enum State { // basically same enums defined in different classes Running, Stopped, Broken } } } } What is needed is unified enum State for both classes that is seen to outside world alongside with safe type conversion. The best and probably most straightforward way I came up with is to create external enum: enum State { Running, Stopped, Broken } together with conversion functions State stateEnumConv(A::B::CarInfo::State aState); State stateEnumConv(A::B::BikeInfo::State aState); A::B::CarInfo::State stateEnumConv(State aState); A::B::BikeInfo::State stateEnumConv(State aState); Direction into right approach is needed. Gosh coming from C I hate those long namespaces everywhere an I wish it could be only A::B level like in presented example. Four conversion functions seem redundant note that CarInfo::State and BikeInfo::State has same enum "members".

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  • update query with join on two tables

    - by dba_query
    I have customer and address tables. query: select * from addresses a, customers b where a.id = b.id returns 474 records For these records, I'd like to add the id of customer table into cid of address table. Example: If for the first record the id of customer is 9 and id of address is also 9 then i'd like to insert 9 into cid column of address table. I tried: update addresses a, customers b set a.cid = b.id where a.id = b.id but this does not seem to work.

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  • JOIN in SQL with one-to-many relationship

    - by Kristopher Ives
    I'm making a tool to track calls to house/senate reps, and I have 2 tables of importance here: reps rep_id rep_name # and more info comments rep_id status # enum about result of contact comment I want to query for all reps joining the most recent associated comments and in some cases joining comments of a specific status, but there might not be any comments associated with that rep yet. THANKS!

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  • [PHP] md5(uniqid) makes sense for random unique tokens?

    - by Exception e
    I want to create a token generator that generates tokens that cannot be guessed by the user and that are still unique (to be used for password resets and confirmation codes). I often see this code; does it make sense? md5(uniqid(rand(), true)); According to a comment uniqid($prefix, $moreEntopy = true) yields first 8 hex chars = Unixtime, last 5 hex chars = microseconds. I don't know how the $prefix-parameter is handled.. So if you don't set the $moreEntopy flag to true, it gives a predictable outcome. QUESTION: But if we use uniqid with $moreEntopy, what does hashing it with md5 buy us? Is it better than: md5(mt_rand())

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  • self join to select consecutive numbers

    - by shantanuo
    CREATE TABLE `mybug` ( `SEAT_NO` decimal(2,0) NOT NULL, `ROW_NO` decimal(2,0) NOT NULL, `COL_NO` decimal(2,0) NOT NULL ) ENGINE=MyISAM DEFAULT CHARSET=latin1; INSERT INTO `mybug` VALUES ('1','1','1'),('26','7','2'),('31','8','2'),('32','8','1'),('33','9','1'),('34','9','2'),('35','9','5'),('36','9','6'),('37','10','6'),('38','10','5'),('39','10','2'),('40','10','1'),('41','11','1'),('42','11','2'),('43','11','4'),('44','11','5'); +---------+--------+--------+ | SEAT_NO | ROW_NO | COL_NO | +---------+--------+--------+ | 1 | 1 | 1 | | 26 | 7 | 2 | | 31 | 8 | 2 | | 32 | 8 | 1 | | 33 | 9 | 1 | | 34 | 9 | 2 | | 35 | 9 | 5 | | 36 | 9 | 6 | | 37 | 10 | 6 | | 38 | 10 | 5 | | 39 | 10 | 2 | | 40 | 10 | 1 | | 41 | 11 | 1 | | 42 | 11 | 2 | | 43 | 11 | 4 | | 44 | 11 | 5 | +---------+--------+--------+ 16 rows in set (0.00 sec) In the above chart, I need to select 2 seats those are in the same row AND column numbers are next to each other. For e.g. Seat Numbers 38 & 39 can not be issued even if both the seats are from the same row because the column numbers 2 & 5 are not adjacent. The expected results are as follows: 31 33 35 37 39 41 43 These are the starting numbers and the next seat will be automatically booked as well. for e.g. 31 & 32

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  • Problem in Union Join For MySQL Query

    - by Mac Taylor
    hey guys i managed to select from a table that saves my latest posts but i need to have double condition in selection here is my code : $sql_query = "SELECT b.*,u.username AS MY_Sender FROM TABLE_users u,TABLE_blogs b Where b.reciever = '0' AND u.user_id = b.sender UNION SELECT b.*,u.username AS MY_reciever FROM TABLE_users u,TABLE_blogs b Where b.reciever != '0' AND u.user_id = b.reciever ORDER BY bid DESC LIMIT 0,7 "; but MY_reciever is Null and empty Am i wrong in using UNION for this need ?!

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