php - How to insert data in the nested set model(MySQL); -


in nested set model have left , right columns

the first time when table empty, need insert right column, if don't know how many children have

left 1 - forever

right ? - value goes here??

how make dynamic? not static.

ps: using php

i'm assuming tags , title looking solution works mysql.

yes, right unless know number of elements in advance value right needs calculated dynamically. there 2 approaches can use:

  • you start least value works (2 in case) , increase later needed.
  • you make guess 10000000 , hope that's enough, need prepared possibility wasn't enough , may need adjusting again later.

in both cases need implement left , right values multiple rows may need adjusted when inserting new rows, in second case need perform updates if guesses wrong. second solution more complex, can give better performance.

note of 4 common ways store heirarchical data, nested sets approach hardest perform inserts , updates. see slide 69 of bill karwin's models heirarchical data.

nested sets update difficulty


Comments

Post a Comment

Popular posts from this blog

javascript - backbone.js Collection.add() doesn't `construct` (`initialize`) an object -

<!doctype html public "-//w3c//dtd xhtml 1.0 strict//en" "http://www.w3.org/tr/xhtml1/dtd/xhtml1-strict.dtd"> <html> <head> <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js"></script> <script src="http://documentcloud.github.com/underscore/underscore-min.js"></script> <script src="http://documentcloud.github.com/backbone/backbone-min.js"></script> </head> <body> <button id="cmd_create_event" name="cmd_create_event" type="button">create new `event`</button> <script type="text/javascript"> var eventmodel = backbone.model.extend({ initialize : function() { console.log("`event` initialized. id: " + this.cid); this.bind("change:status", function() { console.log(this.get("status") + " value `status`"); }); this.bind("error", function(model, e...
Read more

php - Get uncommon values from two or more arrays -

is there function in php give array of uncommon values 2 or more arrays? for example: $array1 = array( "green", "red", "blue"); $array2 = array( "green", "yellow", "red"); .... $result = function_needed($array1, $array2,...); print_r($result); should give output: array("blue", "yellow", ...); use array_diff , array_merge : $result = array_merge(array_diff($array1, $array2), array_diff($array2, $array1)); here's demo. for multiple arrays, combine callback , array_reduce : function unique(&$a, $b) { return $a ? array_merge(array_diff($a, $b), array_diff($b, $a)) : $b; } $arrays = array( array('green', 'red', 'blue'), array('green', 'yellow', 'red') ); $result = array_reduce($arrays, 'unique'); and here's demo of that.
Read more

Adding duplicate array rows in Php -

i create function in php adds rows of array shared column value. so input. $test = array( array("c", 5, 6), array("c", 2, 3), array("test", 5, 6) ); and output. $testduplicatefree = array( array("c", 7, 9), array("test", 5, 6) ) ); i'm thinking function combine_duplicates($array,$col){ ... ... return $duplicatefreearray; } where $col duplicate free array. so, in case, combine_duplicates($test,0); would me desired output. this. <?php function combine_duplicates($array,$col) { $index = array(); foreach ($array $row) { $key = $row[$col]; if (!isset($index[$key])) { $index[$key] = $row; } else { ($i = 0; $i < count($row); ++$i) { if ($i != $col) { $index[$key][$i] += $row[$i]; } } } } return array_values($index); } $array = array( array("c", 5, 6), array("c", 2, 3), array("test", 5, 6) ); print_r(combine_duplicates($array, 0)); try here: http://codepad.org/mdhesqhi
Read more