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  • Does Ruby on Rails "has_many" array provide data on a "need to know" basis?

    - by Jian Lin
    On Ruby on Rails, say, if the Actor model object is Tom Hanks, and the "has_many" fans is 20,000 Fan objects, then actor.fans gives an Array with 20,000 elements. Probably, the elements are not pre-populated with values? Otherwise, getting each Actor object from the DB can be extremely time consuming. So it is on a "need to know" basis? So does it pull data when I access actor.fans[500], and pull data when I access actor.fans[0]? If it jumps from each record to record, then it won't be able to optimize performance by doing sequential read, which can be faster on the hard disk because those records could be in the nearby sector / platter layer -- for example, if the program touches 2 random elements, then it will be faster just to read those 2 records, but what if it touches all elements in random order, then it may be faster just to read all records in a sequential way, and then process the random elements. But how will RoR know whether I am doing only a few random elements or all elements in random?

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  • Java MySQL Query Problem MySQLSyntaxErrorException When Creating a Table

    - by Aqib Mushtaq
    I fairly new to MySQL with Java, but I have executed a few successful INSERT queries however cannot seem to get the CREATE TABLE query to execute without getting the 'MySQLSyntaxErrorException' exception. My code is as follows: import java.sql.*; Statement stmt; Class.forName("com.mysql.jdbc.Driver"); String url = "jdbc:mysql://localhost:3306/mysql"; Connection con = DriverManager.getConnection(url, "root", "password"); stmt = con.createStatement(); String tblSQL = "CREATE TABLE IF NOT EXISTS \'dev\'.\'testTable\' (\n" + " \'id\' int(11) NOT NULL AUTO_INCREMENT,\n" + " \'date\' smallint(6) NOT NULL\n" + ") ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;"; stmt.executeUpdate(tblSQL); stmt.close(); con.close(); And the error is as follows: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ''dev'.'testTable' ( 'id' int(11) NOT NULL AUTO_INCREMENT, 'date' smallint(6) N' at line 1 I would appreciate it if anyone could spot the mistake in this query, as I've tried executing this within phpMyAdmin and it works as it should. Thanks in advance.

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  • What is a good DBMS for archiving?

    - by Thomas.Winsnes
    I've been stuck in a MsSql/MySql world now for a few years, and I've decided to spread my wings a little further. At the moment I'm researching which DBMS is good at things needed when archiving data. Eg. lots of writes and low reads. I've seen the NoSQL crusade, but I have a very RDBMS mindset, so I'm a bit skeptical. Anyone have any suggestions? Or even any pointers to where there are some benchmarks etc for this kind of stuff. Thank you :) Thomas

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  • Is copying /var/lib/mysql a good alterntive to mysqldump?

    - by kemp
    Since I'm making a full backup of my entire debian system, I was thinking if having a copy of /var/lib/mysql directory is a viable alternative to dumping tables with mysqldump. are all informations needed contained in that directory? can single tables be imported in another mysql? can there be problems while restoring those files on a (probably slightly) different mysql server version?

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  • What's the best way to migrate a Django DB from SQLite to MySQL?

    - by Inshim
    I need to migrate my db from sqlite to mysql, and the various tools/scripts out there are too many for me to easily spot the safest and most elegant solution. This seemed to me nice http://djangosnippets.org/snippets/14/ but appears to be 3 years since getting an update which is worrying.. Can you recommend a solution that is known to be reliable with Django 1.1.1 ?

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  • PHP won't parse MySQL statements

    - by Hussain
    I just installed Apache 2.2.15/PHP 5.3.2/MySQL 5.1.44 on Windows Vista. Apache is working fine, PHP is functional, and MySQL works on the CLI. However, when I try to access MySQL via PHP, I get an error (Fatal error: Call to undefined function mysql_connect()). extension=php_mysql.dll and extension=php_mbstring.dll are uncommented in the php.ini file, and PHP is in the system path. There is no libmysql.dll in either the top level PHP directory or the ext directory. There's a libmySQL.dll file in the MySQL bin directory (which is also in the system path); I tried renaming it, but that doesn't do anything Also, in case anyone wants to know, I originally installed PHP using the MSI installer, but it was missing some DLLs, so I installed from the zip file. I think I've exhausted all my options. Any help on this problem would be very appreciated. Thanks in advance.

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  • Problem with mysql query to replace a string

    - by alex
    I've used mysql's update replace function before, but even though I think I'm following the same syntax, I can't get this to work. Here's what I'm trying to do: UPDATE contained_widgets SET preference_values = REPLACE(preference_values, '<li><a_href="/enewsletter"><span class="not-tc">eNewsletter</span></a></li>', '<li><a_href="/enewsletter"><span class="not-tc">eNewsletter</span></a></li> <li> <a_href="/projects"><span class="not-tc">Projects</span></a></li>'); Query OK, 0 rows affected (0.00 sec) Rows matched: 77 Changed: 0 Warnings: 0 I don't see what I'm missing. Any help is appreciated. I edited "a " to "a_" because the site thinks I'm posting spam links otherwise.

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  • How to make msbuild ItemGroup items be separated with a space rather than semi-colon?

    - by mark
    Dear ladies and sirs. Observe the following piece of an msbuild script: <ItemGroup> <R Include="-Microsoft.Design#CA1000" /> <R Include="-Microsoft.Design#CA1002" /> </ItemGroup> I want to convert it to /ruleid:-Microsoft.Design#CA1000 /ruleid:-Microsoft.Design#CA1002 Now, the best I came up with is @(R -> '/ruleid:%(Identity)'), but this only yields /ruleid:-Microsoft.Design#CA1000;/ruleid:-Microsoft.Design#CA1002 Note the semi-colon separating the two rules, instead of a space. This is bad, it is not recognized by the fxcop - I need a space there. Now, this is a simple example, so I could just declare something like this: <PropertyGroup> <R>/ruleid:-Microsoft.Design#CA1000 /ruleid:-Microsoft.Design#CA1002</R </PropertyGroup> But, I do not like this, because in reality I have many rules I wish to disable and listing all of them like this is something I wish to avoid.

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  • PHP mySQL - replace some string inside string

    - by apis17
    i want to replace ALL comma , into ,<space> in all address table in my mysql table. For example, +----------------+----------------+ | Name | Address | +----------------+----------------+ | Someone name | A1,Street Name | +----------------+----------------+ Into +----------------+----------------+ | Name | Address | +----------------+----------------+ | Someone name | A1, Street Name| +----------------+----------------+ Thanks in advance.

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  • Datamapper Clone Record w/ New ID

    - by BouncePast
    class Item include DataMapper::Resource property :id, Serial property :title, String end item = Item.new(:title = 'Title 1') # :id = 1 item_clone = Item.first(:id = 1).clone item_clone.save This does "clone" the object as described but how can this be done so it applies a different ID once the record is saved, e.g. #

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  • YAHOO QUERY LANGUAGE BUG!

    - by Damiano
    Hello everybody! Today, I've started with Yahoo Query Language. I would use it to retrive stocks details, so I'm talking about Yahoo Finance. I think there is a bug on this language. This is my query: select * from yahoo.finance.quoteslist where symbol='@^GSPC' I ALWAYS get 51 results! it's impossible, take a look at: http://it.finance.yahoo.com/q/cp?s=^GSPC There are 500 results! I also tried some paging parameters. select * from yahoo.finance.quoteslist(50,30) where symbol='@^GSPC' (to get from 50 to 80) select * from yahoo.finance.quoteslist(100) where symbol='@^GSPC' (to get the first 100 results) select * from yahoo.finance.quoteslist where symbol='@^GSPC' limit 30 offset 50 but ALWAYS the last stock is: <quote symbol="BBY"> <Symbol>BBY</Symbol> <LastTradePriceOnly>41.03</LastTradePriceOnly> <LastTradeDate>5/7/2010</LastTradeDate> <LastTradeTime>4:00pm</LastTradeTime> <Change>-0.48</Change> <Open>41.35</Open> <DaysHigh>42.35</DaysHigh> <DaysLow>39.60</DaysLow> <Volume>14129531</Volume> </quote> Why do I have this kind of problem? Thank you so much for your support! (P.S. I've tested it on Yahoo YQL console)

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  • Single Large v/s Multiple Small MySQL tables for storing Options

    - by Prasad
    Hi there, I'm aware of several question on this forum relating to this. But I'm not talking about splitting tables for the same entity (like user for example) Suppose I have a huge options table that stores list options like Gender, Marital Status, and many more domain specific groups with same structure. I plan to capture in a OPTIONS table. Another simple option is to have the field set as ENUM, but there are disadvantages of that as well. http://www.brandonsavage.net/why-you-should-replace-enum-with-something-else/ OPTIONS Table: option_id <will be referred instead of the name> name value group Query: select .. from options where group = '15' - Since this table is expected to be multi-tenant, the no of rows could grow drastically. - I believe splitting the tables instead of finding by the group would be easier to write & faster to execute. - or perhaps partitioning by the group or tenant? Pl suggest. Thanks

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  • Do non-clustered indexes slow down inserts?

    - by mikeinmadison
    I'm working in Sql Server 2005. I have an event log table that tracks user actions, and I want to make sure that inserts into the table are as fast as possible. Currently the table doesn't have any indexes. Does adding a single non-clustered index slow down inserts at all? Or is it only clustered indexes that slow down inserts? Or should I just add a clustered index and not worry about it?

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  • Reading directly from the Doctrine Searchable index table

    - by phidah
    I've got a Doctrine table with the Searchable behavior enabled. Whenever a record is created, an index is made in another table. I have a model called Entry and the behavior automatically created the table entry_index. My question now is: How can I - without using the search(...) methods of my model use the data from this table? I want to create a tag cloud of the words most used, and the data in the index table is exactly what I need.

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  • Is it possible to combine these 3 mySQL queries?

    - by Greenie
    I know the $downloadfile - and I want the $user_id. By trial and error I found that this does what I want. But it's 3 separate queries and 3 while loops. I have a feeling there is a better way. And yes, I only have a very little idea about what I'm doing :) $result = pod_query("SELECT ID FROM wp_posts WHERE guid LIKE '%/$downloadfile'"); while ($row = mysql_fetch_assoc($result)) { $attachment = $row['ID']; } $result = pod_query("SELECT pod_id FROM wp_pods_rel WHERE tbl_row_id = '$attachment'"); while ($row = mysql_fetch_assoc($result)) { $pod_id = $row['pod_id']; } $result = pod_query("SELECT tbl_row_id FROM wp_pods_rel WHERE tbl_row_id = '$pod_id' AND field_id = '28'"); while ($row = mysql_fetch_assoc($result)) { $user_id = $row['pod_id']; }

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  • wanting to move up from ms access, thinking .net? visual studio?

    - by Tristan Lear
    So I wrote a project-management program for a small business using Microsoft Access 2007. Now they've requested lots of additional features (timekeeping, privileged data tiers ...) I personally use Linux, but the whole office uses Windows. I'm relatively new to programming but like to teach myself using projects like this. I'm right on the edge on this -- I can't really tell what the path of least resistance here is: do I stay in access + VBA and teach myself a dying, annoying language -- while struggling against all the limitations of Access? Or do I move to something else? Python seems simple enough ... Whatever I use, i need to be able to offer a GUI.

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  • How do I add a one-to-one relationship in MYSQL?

    - by alex
    +-------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+-------------+------+-----+---------+-------+ | pid | varchar(99) | YES | | NULL | | +-------+-------------+------+-----+---------+-------+ 1 row in set (0.00 sec) +-------+---------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+---------------+------+-----+---------+-------+ | pid | varchar(2000) | YES | | NULL | | | recid | varchar(2000) | YES | | NULL | | +-------+---------------+------+-----+---------+-------+ 2 rows in set (0.00 sec) This is my table. pid is just the id of the user. "recid" is a recommended song for that user. I hope to have a list of pid's, and then recommended songs for each person. Of course, in my 2nd table, (pid, recid) would be unique key. How do I do a one-to-one query for this ?

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  • Rails, search item in different model?

    - by Danny McClelland
    Hi Everyone, I have a kase model which I am using a simple search form in. The problem I am having is some kases are linked to companies through a company model, and people through a people model. At the moment my search (in Kase model) looks like this: # SEARCH FACILITY def self.search(search) search_condition = "%" + search + "%" find(:all, :conditions => ['jobno LIKE ? OR casesubject LIKE ? OR transport LIKE ? OR goods LIKE ? OR comments LIKE ? OR invoicenumber LIKE ? OR netamount LIKE ? OR clientref LIKE ? OR kase_status LIKE ? OR lyingatlocationaddresscity LIKE ?', search_condition, search_condition, search_condition, search_condition, search_condition, search_condition, search_condition, search_condition, search_condition, search_condition]) end What I am trying to work out, is what condition can I add to allow a search by Company or Person to show the cases they are linked to. @kase.company.companyname and company.companyname don't work :( Is this possible? Thanks, Danny

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