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• Should foreign keys become table primary key?

  - by Carvell Fenton

  Hello again, I have a table (session_comments) with the following fields structure: student_id (foreign key to students table) session_id (foreign key to sessions table) session_subject_ID (foreign key to session_subjects table) user_id (foreign key to users table) comment_date_time comment Now, the combination of student_id, session_id, and session_subject_id will uniquely identify a comment about that student for that session subject. Given that combined they are unique, even though they are foreign keys, is there an advantage to me making them the combined primary key for that table? Thanks again.

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• How do you handle descriptive database table names and their effect on foreign key names?

  - by Carvell Fenton

  Hello, I am working on a database schema, and am trying to make some decisions about table names. I like at least somewhat descriptive names, but then when I use suggested foreign key naming conventions, the result seems to get ridiculous. Consider this example: Suppose I have table session_subject_mark_item_info And it has a foreign key that references sessionSubjectID in the session_subjects table. Now when I create the foreign key name based on fk_[referencing_table]__[referenced_table]_[field_name] I end up with this maddness: fk_session_subject_mark_item_info__session_subjects_sessionSubjectID Would this type of a foreign key name cause me problems down the road, or is it quite common to see this? Also, how do the more experienced database designers out there handle the conflict between descriptive naming for readability vs. the long names that result? I am using MySQL and MySQL Workbench if that makes any difference. Thanks!

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• Database design and foreign keys: Where should they be added in related tables?

  - by Carvell Fenton

  I have a relatively simple subset of tables in my database for tracking something called sessions. These are academic sessions (think offerings of a particular program). The tables to represent a sessions information are: sessions session_terms session_subjects session_mark_item_info session_marks All of these tables have their own primary keys, and are like a tree, in that sessions have terms, terms have subjects, subjects have mark items, etc. So each on would have at least its "parent's" foreign key. My question is, design wise is it a good idea to include the sessions primary key in the other tables as a foreign key to easily select related session items, or is that too much redundency? If I include the session foreign key (or all parent foreign keys from tables up the heirarchy) in all the tables, I can easily select all the marks for a session. As an example, something like SELECT mark FROM session_marks WHERE sessionID=... If I don't, then I would have to combine selects with something like WHERE something IN (SELECT... Which approach is "more correct" or efficient? Thanks in advance!

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• Is there a recommended approach to handle saving data in response to within-site navigation without

  - by Carvell Fenton

  Hello all, Preamble to scope my question: I have a web app (or site, this is an internal LAN site) that uses jQuery and AJAX extensively to dynamically load the content section of the UI in the browser. A user navigates the app using a navigation menu. Clicking an item in the navigation menu makes an AJAX call to php, and php then returns the content that is used to populate the central content section. One of the pages served back by php has a table form, set up like a spreadsheet, that the user enters values into. This table is always kept in sync with data in the database. So, when the table is created, is it populated with the relevant database data. Then when the user makes a change in a "cell", that change immediately is written back to the database so the table and database are always in sync. This approach was take to reassure users that the data they entered has been saved (long story...), and to alleviate them from having to click a save button of some kind. So, this always in sync idea is great, except that a user can enter a value in a cell, not take focus out of the cell, and then take any number of actions that would cause that last value to be lost: e.g. navigate to another section of the site via the navigation menu, log out of the app, close the browser, etc. End of preamble, on to the issue: I initially thought that wasn't a problem, because I would just track what data was "dirty" or not saved, and then in the onunload event I would do a final write to the database. Herein lies the rub: because of my clever (or not so clever, not sure) use of AJAX and dynamically loading the content section, the user never actually leaves the original url, or page, when the above actions are taken, with the exception of closing the browser. Therefore, the onunload event does not fire, and I am back to losing the last data again. My question, is there a recommended way to handle figuring out if a person is navigating away from a "section" of your app when content is dynamically loaded this way? I can come up with a solution I think, that involves globals and tracking the currently viewed page, but I thought I would check if there might be a more elegant solution out there, or a change I could make in my design, that would make this work. Thanks in advance as always!

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• PHP, MySQL prepared statements - can you use results of execute more than once by calling data_seek(

  - by Carvell Fenton

  Hello, I have a case where I want to use the results of a prepared statement more than once in a nested loop. The outer loop processes the results of another query, and the inner loop is the results of the prepared statement query. So the code would be something like this (just "pseudoish" to demonstrate the concept): // not showing the outer query, it is just a basic SELECT, not prepared statement // we'll call it $outer_query $obj_array = array(); // going to save objects in this $ids = array(18,19,20); // just example id numbers $query = "SELECT field1, field2 FROM table1 WHERE id=?"; $stmt = $db->prepare($query); foreach ($ids as $id) { $stmt->bind_param("i", $id); $stmt->execute(); $stmt->bind_result($var1, $var2); $stmt->store_result(); // I think I need this for data_seek while ($q1 = $outer_query->fetch_object()) { while ($stmt->fetch()) { if ($q1->field1 == $var1) { // looking for a match $obj = new stdClass(); $obj->var1 = $var1; $obj->var2 = $var2; $obj_array[] = $obj; $stmt->data_seek(0); // reset for outer loop break; // found match, so leave inner } } } } The problem I seem to be experiencing is that the values are not getting bound in the variables as I would expect after the first time I use fetch in the inner loop. Specifically, in one example I ran with 3 ids for the foreach, the first id was processed correctly, the second was processed incorrectly (matches were not found in the inner loop even though they existed), and then the third was processed correctly. Is there something wrong with the prepared statment function calls in the sequence I am doing above, or is this an invalid way to use the results of the prepared statement? Thanks.

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• PHP MySQLi and MySQLi_STMT: Which insert_id to use?

  - by Carvell Fenton

  Hello all, Both the MySQLi and MySQLi_STMT classes have an $insert_id property. If I am connected to my database using a MySQLi object (say $db), and then I perform an INSERT with a MySQLi_STMT object (say $stmt), to get the id of the last INSERT, should I use: $last_id = $db->insert_id; or $last_id = $stmt->insert_id; Or would they be the same, in which case it doesn't matter? I thought this might be a quick answer for someone, and save me the time of writing the test code to check it. Thanks in advance as always.

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• Free E-Book - TypeScript Succinctly

  - by TATWORTH

  Originally posted on: http://geekswithblogs.net/TATWORTH/archive/2013/06/22/free-e-book---typescript-succinctly.aspxAt http://www.syncfusion.com/resources/techportal/ebooks/typescript, Syncfusion are a free E-book "TypeScript Succinctly""The extensive adoption of JavaScript for application development, and the ability to use HTML and JavaScript to create Windows Store apps, led Microsoft to develop TypeScript, a superset of JavaScript. Though the messiness of JavaScript causes many .NET developers to avoid the language, Microsoft's additions extend many familiar features of .NET programming to JavaScript. With TypeScript Succinctly by Steve Fenton, you will learn how TypeScript provides optional static typing and classes to JavaScript development, how to create and load modules, and how to work with existing JavaScript libraries through ambient declarations. TypeScript is even significantly integrated with Visual Studio to provide the autocompletion and type checking you are most comfortable with."

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• IN 'mytextfile.txt' syntax - access

  - by I__

  i would like to use this syntax to update a table in access based on data from a txtfile. fenton in his comments on this answer: http://stackoverflow.com/questions/2992168/read-text-file-line-by-line-and-insert-update-values-in-table/2992337#2992337 said that this is possible and i would like to see the exact syntax please

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• question about frequency of updating access

  - by I__

  i have a table in an access database this access database is used on a regular basis, basically from 9-5 someone else has a copy of this exact table. sometimes records are added, sometimes deleted, and sometimes data within the records is updated. i need to update the access database table with the offsite table every hour or so. what is the best algorithm of updating the data? there are about 5000 records. would it severely lock up the table for a few seconds every hour? i would like to publicly apologize for my rude comment to david fenton

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• Simple Grouping With TableSorter Plugin

  - by HurnsMobile

  Im playing around with the Tablesorter plug-in for jQuery and was trying to get a very simple grouping functionality added into it. Using the follow html/js works great until you click sort again and reverse the order. The headers get moved to the bottom of the group when this happens. The following is my (admitedly hacky) attempt at it. Does anyone have any ideas? <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" /> <title>Table Manipulation Test</title> <link type="text/css" href="css/ui-lightness/jquery-ui-1.8.1.custom.css" rel="stylesheet" /> <link rel="stylesheet" href="tablesorter/themes/green/style.css" type="text/css"/> <script type="text/javascript" src="js/jquery-1.4.2.min.js"></script> <script type="text/javascript" src="js/jquery-ui-1.8.1.custom.min.js"></script> <script type="text/javascript" src="tablesorter/jquery.tablesorter.min.js"></script> <script type="text/javascript"> $(document).ready(function() { $("#test_table").tablesorter({ sortForce: [[3,0]] }); $(".group_details").hide(); $(".group_header").click(function(){ var group = $(this).attr("group"); var $expander = $(this).children("td.expanderguy") if ($("." + group + ":visible").length){ $("." + group + "").fadeOut('fast'); $expander.html("<img src='icons/plus.gif'>"); } else{ $("." + group + "").fadeIn('fast'); $expander.html("<img src='icons/minus.gif'>"); } }); } ); </script> <style type="text/css"> .group_header td{ background-color: #888888; !important } </style> </head> <body> <table id="test_table" class="tablesorter"> <thead> <tr><th>First Name</th><th>Last Name</th><th>Email</th><th>Due Date</th><th>Amount Due</th></tr> </thead> <tbody> <tr class="group_header" group="group1"><td class="expanderguy"><img src="icons/plus.gif"></td><td></td><td></td><td>Monday, June 7</td><td></td></tr> <tr class="group_details group1"><td>Flavian</td><td>Wenceslas</td><td>[email protected]</td><td>Monday, June 7</td><td>$100</td></tr> <tr class="group_details group1"><td>Gordian</td><td>Ives</td><td>[email protected]</td><td>Monday, June 7</td><td>$1700</td></tr> <tr class="group_details group1"><td>Saladin</td><td>Tarquin</td><td>[email protected]</td><td>Monday, June 7</td><td>$1700</td></tr> <tr class="group_details group1"><td>Urban</td><td>Cyprian</td><td>[email protected]</td><td>Monday, June 7</td><td>$1500</td></tr> <tr class="group_details group1"><td>Sargon</td><td>Swithun</td><td>[email protected]</td><td>Monday, June 7</td><td>$1100</td></tr> <tr class="group_details group1"><td>Pompey</td><td>Ladislas</td><td>[email protected]</td><td>Monday, June 7</td><td>$300</td></tr> <tr class="group_details group1"><td>Attila</td><td>Hiawatha</td><td>[email protected]</td><td>Monday, June 7</td><td>$200</td></tr> <tr class="group_header" group="group2"><td class="expanderguy"><img src="icons/plus.gif"></td><td></td><td></td><td>Tuesday, June 8</td><td></td></tr> <tr class="group_details group2"><td>Bruce</td><td>Fenton</td><td>[email protected]</td><td>Tuesday, June 8</td><td>$1700</td></tr> <tr class="group_details group2"><td>Wade</td><td>Sequoia</td><td>[email protected]</td><td>Tuesday, June 8</td><td>$1400</td></tr> <tr class="group_details group2"><td>Eddie</td><td>Jerold</td><td>[email protected]</td><td>Tuesday, June 8</td><td>$1100</td></tr> <tr class="group_details group2"><td>Lynn</td><td>Lucan</td><td>[email protected]</td><td>Tuesday, June 8</td><td>$1200</td></tr> <tr class="group_details group2"><td>Taegan</td><td>Tadg</td><td>[email protected]</td><td>Tuesday, June 8</td><td>$100</td></tr> <tr class="group_details group2"><td>Clyde</td><td>Reed</td><td>[email protected]</td><td>Tuesday, June 8</td><td>$6100</td></tr> <tr class="group_details group2"><td>Alaois</td><td>Art</td><td>[email protected]</td><td>Tuesday, June 8</td><td>$2100</td></tr> <tr class="group_details group2"><td>Gilbert</td><td>Patsy</td><td>[email protected]</td><td>Tuesday, June 8</td><td>$1500</td></tr> <tr class="group_header" group="group3"><td class="expanderguy"><img src="icons/plus.gif"></td><td></td><td></td><td>Wednesday, June 9</td><td></td></tr> <tr class="group_details group3" ><td>Clem</td><td>Eben</td><td>[email protected]</td><td>Wednesday, June 9</td><td>$2100</td></tr> <tr class="group_details group3" ><td>Elijah</td><td>Julyan</td><td>[email protected]</td><td>Wednesday, June 9</td><td>$2100</td></tr> <tr class="group_details group3" ><td>Marvyn</td><td>Damian</td><td>[email protected]</td><td>Wednesday, June 9</td><td>$1100</td></tr> <tr class="group_details group3" ><td>Sawyer</td><td>Ryker</td><td>[email protected]</td><td>Wednesday, June 9</td><td>$500</td></tr> </tbody> </table> </body>

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