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  • Database localization

    - by Don
    Hi, I have a number of database tables that contain name and description columns which need to be localized. My initial attempt at designing a DB schema that would support this was something like: product ------- id name description local_product ------- id product_id local_name local_description locale_id locale ------ id locale However, this solution requires a new local_ table for every table that contains name and description columns that require localization. In an attempt to avoid this overhead I redesigned the schema so that only a single localization table is needed product ------- id localization_id localization ------- id local_name local_description locale_id locale ------ id locale Here's an example of the data which would be stored in this schema when there are 2 tables (product and country) requiring localization: country id, localization_id ----------------------- 1, 5 product id, localization_id ----------------------- 1, 2 localization id, local_name, local_description, locale_id ------------------------------------------------------ 2, apple, a delicious fruit, 2 2, pomme, un fruit délicieux, 3 2, apfel, ein köstliches Obst, 4 5, ireland, a small country, 2 5, irlande, un petite pay, 3 locale id, locale -------------- 2, en 3, fr 4, de Notice that the compound primary key of the localization table is (id, locale_id), but the foreign key in the product table only refers to the first element of this compound PK. This seems like 'a bad thing' from the POV of normalization. Is there any way I can fix this problem, or alternatively, is there a completely different schema that supports localization without creating a separate table for each localizable table? Update: A number of respondents have proposed a solution that requires creating a separate table for each localizable table. However, this is precisely what I'm trying to avoid. The schema I've proposed above almost solves the problem to my satisfaction, but I'm unhappy about the fact that the localization_id foreign keys only refer to part of the corresponding primary key in the localization table. Thanks, Don

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  • How do I understand the partition table? (I want to start over.)

    - by Sammy Black
    I have Ubuntu 10.04 Lucid installed through wubi on my laptop (it came with Windows 7 preinstalled). This was my first foray into Linux, and I'm here to stay. I have no use for Windows, and yet I must manually choose not to boot into it! Should I shrink the Windows partition to something negligible and grow the Linux one using something like gparted or fdisk, and just be content that everything runs? In that case, I need to understand the filesystems. Which is which? Here's the output of $ df -h: Filesystem Size Used Avail Use% Mounted on /dev/loop0 17G 11G 4.5G 71% / none 1.8G 300K 1.8G 1% /dev none 1.8G 376K 1.8G 1% /dev/shm none 1.8G 316K 1.8G 1% /var/run none 1.8G 0 1.8G 0% /var/lock none 1.8G 0 1.8G 0% /lib/init/rw /dev/sda3 290G 50G 240G 18% /host I would prefer to start over with a clean install of 10.10 Maverick, but I fear what I may lose. Certainly, I will backup my home directory tree (gzip?), but what about various pieces of software that I've acquired from the repositories? Can I keep a record of them? By the way, I asked a similar question over on Ubuntu forums.

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  • Adding defaults and indexes to a script/generate command in a Rails Template?

    - by charliepark
    I'm trying to set up a Rails Template that would allow for comprehensive set-up of a specific Rails app. Using Pratik Naik's overview (http://m.onkey.org/2008/12/4/rails-templates), I was able to set up a couple of scaffolds and models, with a line that looks something like this ... generate("scaffold", "post", "title:string", "body:string") I'm now trying to add in Delayed Jobs, which normally has a migration file that looks like this: create_table :delayed_jobs, :force => true do |table| table.integer :priority, :default => 0 # Allows some jobs to jump to the front of the queue table.integer :attempts, :default => 0 # Provides for retries, but still fail eventually. table.text :handler # YAML-encoded string of the object that will do work table.text :last_error # reason for last failure (See Note below) table.datetime :run_at # When to run. Could be Time.now for immediately, or sometime in the future. table.datetime :locked_at # Set when a client is working on this object table.datetime :failed_at # Set when all retries have failed (actually, by default, the record is deleted instead) table.string :locked_by # Who is working on this object (if locked) table.timestamps end So, what I'm trying to do with the Rails template, is to add in that :default = 0 into the master template file. I know that the rest of the template's command should look like this: generate("migration", "createDelayedJobs", "priority:integer", "attempts:integer", "handler:text", "last_error:text", "run_at:datetime", "locked_at:datetime", "failed_at:datetime", "locked_by:string") Where would I put (or, rather, what is the syntax to add) the :default values in that? And if I wanted to add an index, what's the best way to do that?

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  • Association Mapping Details confusion?

    - by AaronLS
    I have never understood why the associations in EntityFramework look the way they do in the Mapping Details window. When I select the line between 2 tables for an association, for example FK_ApplicationSectionsNodes_FormItems, it shows this: Association Maps to ApplicationSectionNodes FormItems (key symbol) FormItemId:Int32 <--> FormItemId:int ApplicationSectionNodes (key symbol) NodeId:Int32 <--> (key symbol) NodeId : int Fortunately this one was create automatically for me based on the foreign key constraints in my database, but whenever no constraints exist, I have a hard to creating associations manually(when the database doesn't have a diagram setup) because I don't understand the mapping details for associations. FormItems table has a primary key identity column FormItemId, and ApplicationSectionNodes contains a FormItemId column that is the foreign key and has NodeId as a primary key identity column. What really makes no sense to me is why the association has anything listed about the NodeId, when NodeId doesn't have anything to do with the foreign key relationship? (It's even more confusing with self referencing relationships, but maybe if I could understand the above case I'd have a better handle). CREATE TABLE [dbo].[ApplicationSectionNodes]( [NodeID] [int] IDENTITY(1,1) NOT NULL, [OutlineText] [varchar](5000) NULL, [ParentNodeID] [int] NULL, [FormItemId] [int] NULL, CONSTRAINT [PK_ApplicationSectionNodes] PRIMARY KEY CLUSTERED ( [NodeID] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY], CONSTRAINT [UQ_ApplicationSectionNodesFormItemId] UNIQUE NONCLUSTERED ( [FormItemId] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] GO ALTER TABLE [dbo].[ApplicationSectionNodes] WITH NOCHECK ADD CONSTRAINT [FK_ApplicationSectionNodes_ApplicationSectionNodes] FOREIGN KEY([ParentNodeID]) REFERENCES [dbo].[ApplicationSectionNodes] ([NodeID]) GO ALTER TABLE [dbo].[ApplicationSectionNodes] NOCHECK CONSTRAINT [FK_ApplicationSectionNodes_ApplicationSectionNodes] GO ALTER TABLE [dbo].[ApplicationSectionNodes] WITH NOCHECK ADD CONSTRAINT [FK_ApplicationSectionNodes_FormItems] FOREIGN KEY([FormItemId]) REFERENCES [dbo].[FormItems] ([FormItemId]) GO ALTER TABLE [dbo].[ApplicationSectionNodes] NOCHECK CONSTRAINT [FK_ApplicationSectionNodes_FormItems] GO FormItems Table: CREATE TABLE [dbo].[FormItems]( [FormItemId] [int] IDENTITY(1,1) NOT NULL, [FormItemType] [int] NULL, CONSTRAINT [PK_FormItems] PRIMARY KEY CLUSTERED ( [FormItemId] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] GO ALTER TABLE [dbo].[FormItems] WITH NOCHECK ADD CONSTRAINT [FK_FormItems_FormItemTypes] FOREIGN KEY([FormItemType]) REFERENCES [dbo].[FormItemTypes] ([FormItemTypeId]) GO ALTER TABLE [dbo].[FormItems] NOCHECK CONSTRAINT [FK_FormItems_FormItemTypes] GO

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  • How do you resolve the common naming collision between type and object?

    - by Catskul
    Since the standard c# convention is to capitalize the first letter of public properties, the old c++ convention of initial capital for type names, and initial lowercase for non-type names does not prevent the classic name collision where the most obvious object name matches the type name: class FooManager { public BarManager BarManager { get; set; } // Feels very wrong. // Recommended naming convention? public int DoIt() { // 1st and 2nd Bar Manager are different symbols return BarManager.Blarb + BarManager.StaticBlarb; } } class BarManager { public int Blarb { get; set; } public static int StaticBlarb { get; set; } } It seems to compile, but feels so wrong. Is there a recommend naming convention to avoid this?

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  • SQL DB design to support user feeds (in application like facebook)

    - by Yoav
    I have a social network server with a MySql DB. I want to show the users feeds like done in Facebook. Example - UserX now Friend with userY, userX did like on postX etc. Currently I have table: C1 : UserId C2 : LogType (now friend, did like etc) C3 : ObjectId (Can be userId or postId) - set depending on the LogType. Currently to get all related logs to show to the user I do the following queries: 1. Get All user Friends userIds 2. Query all rows which C1 is in userIds (I query completed) 3. Scan the DB and see - if LogType equals DidLike, check if post's OwnerId is the userId - if yes add it to logs. And so on. Obvious this is not efficient at all. I am looking for a better way. I thought I had in mind: Create a new table (in addition to the Log table) C1 : UserId C2 : LogId (from Log table) C3 : UserID of the one who did the action When querying logs - look in the table and get related Logs (by LogId) from LogTable. Updating the table: Whenever user doing action that should be in the log: 1. Add the Log entry to LogTable. 2. Scan the DB and see which users are interested with the Log (Who my friends are, Who is the owner of the post) and add related entries to the new table. (must be done in BG). 3. If user UNFRIEND another user - then look in the logs for all rows where C3 == UNFRIENDED user id and delete them. Any opinions? Other suggestions?

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  • Is it Possible to Use Constraints on Hierarchical Data in a Self-Referential Table?

    - by pbarney
    Suppose you have the following table, intended to represent hierarchical data: +--------+-------------+ | Field | Type | +--------+-------------+ | id | int(10) | | parent | int(10) | | name | varchar(45) | +--------+-------------+ The table is self-referential in that the parent_id refers to id. So you might have the following data: +----+--------+---------------+ | id | parent | name | +----+--------+---------------+ | 1 | 0 | fruit | | 2 | 0 | vegetable | | 3 | 1 | apple | | 4 | 1 | orange | | 5 | 3 | red delicious | | 6 | 3 | granny smith | | 7 | 3 | gala | +----+--------+---------------+ Using MySQL, I am trying to impose a (self-referential) foreign key constraint upon the data to cascade on update and prevent deletion of a record if it has any "children." So I used the following: CREATE TABLE `test`.`fruit` ( `id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT, `parent` INT(10) UNSIGNED, `name` VARCHAR(45) NOT NULL, PRIMARY KEY (`id`), CONSTRAINT `fk_parent` FOREIGN KEY (`parent`) REFERENCES `fruit` (`id`) ON UPDATE CASCADE ON DELETE RESTRICT ) ENGINE = InnoDB; From what I understand, this should fit my requirements. (And parent must default to null to allow insertions, correct?) The problem is, if I change the id of a record, it will not cascade: Cannot delete or update a parent row: a foreign key constraint fails (`test`.`fruit`, CONSTRAINT `fk_parent` FOREIGN KEY (`parent`) REFERENCES `fruit` (`id`) ON UPDATE CASCADE) What am I missing? Feel free to correct me if my terminology is screwed up... I'm new to constraints.

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  • Entity Framework 5 Enum Naming

    - by Tyrel Van Niekerk
    I am using EF 5 with migrations and code first. It all works rather nicely, but there are some issues/questions I would like to resolve. Let's start with a simple example. Lets say I have a User table and a user type table. The user type table is an enum/lookup table in my app. So the user table has a UserTypeId column and a foreign key ref etc to UserType. In my poco, I have a property called UserType which has the enum type. To add the initial values to the UserType table (or add/change values later) and to create the table in the initial migrator etc. I need a UserType table poco to represent the actual table in the database and to use in the map files. I mapped the UserType property in the User poco to UserTypeId in the UserType poco. So now I have a poco for code first/migrations/context mapping etc and I have an enum. Can't have the same name for both, so do I have a poco called UserType and something else for the enum or have the poco for UserType be UserTypeTable or something? More importantly however, am I missing some key element in how code first works? I tried the example above, ran Add-Migration and it does not add the lookup table for the enum.

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  • How to get XML into a Dictionary with an Expression?

    - by DaveDev
    I have the following XML: <PerformancePanel page="PerformancePanel.ascx" title=""> <FundGroup heading="Net Life Managed Funds"> <fund id="17" countryid="N0" index="24103723" /> <fund id="81" countryid="N0" index="24103723" /> <fund id="127" countryid="N0" index="24103722" /> <fund id="345" countryid="N0" index="24103723" /> <fund id="346" countryid="N0" index="24103723" /> </FundGroup> <FundGroup heading="Net Life Specialist Funds"> <fund id="110" countryid="N0" index="24103717" /> <fund id="150" countryid="N0" index="24103719" /> <fund id="119" countryid="N0" index="24103720" /> <fund id="115" countryid="N0" index="24103727" /> <fund id="141" countryid="N0" index="24103711" /> <fund id="137" countryid="N0" /> <fund id="146" countryid="N0" /> <fund id="133" countryid="N0" /> <fund id="90" countryid="N0" /> <fund id="104" countryid="N0" /> <fund id="96" countryid="N0" /> </FundGroup> </PerformancePanel> I can get the data into an anonymous object as follows: var offlineFactsheet = new { PerformancePanels = (from panel in doc.Elements("PerformancePanel") select new PerformancePanel { PerformanceFunds = (from fg in panel.Elements("FundGroup") select new { Heading = (fg.Attribute("heading") == null) ? "" : (string)fg.Attribute("heading"), Funds = (from fund in fg.Elements("fund") select new Fund { FundId = (int)fund.Attribute("id"), CountryId = (string)fund.Attribute("countryid"), FundIndex = (fund.Attribute("index") == null) ? null : new Index { Id = (int)fund.Attribute("index") }, FundNameAppend = (fund.Attribute("append") == null) ? "" : (string)fund.Attribute("append") }).ToList() }).ToDictionary(xx => xx.Heading, xx => xx.Funds)}; I'm trying to change my code such that I can assign the dictionary directly to a property of the class I'm working in, as described in this question. I'd like to have a Dictionary() where each header text is the key to the list of funds under it. I'm having difficulty applying the example in the linked question because that only returns a string, and this needs to return the dictionary. This is the point that I got to before it occurred to me that I'm lost!!!: this.PerformancePanels = doc.Elements("PerformancePanel").Select(e => { var control = (PerformancePanel)LoadControl(this.OfflineFactsheetPath + (string)e.Attribute("page")); control.PerformanceFunds = e.Elements("FundGroup").Select(f => { List<Fund> funds = (from fund in e.Elements("fund") select new Fund { FundId = (int)fund.Attribute("id"), CountryId = (string)fund.Attribute("countryid"), FundIndex = (fund.Attribute("index") == null) ? null : new Index { Id = (int)fund.Attribute("index") }, FundNameAppend = (fund.Attribute("append") == null) ? "" : (string)fund.Attribute("append") }).ToList(); string heading = (e.Attribute("heading") == null) ? "" : (string)e.Attribute("heading"); }).ToDictionary(xx => heading, xx => Funds); return control; }).ToList(); Could someone point me in the right direction please? I'm not even sure if 'Expression' is the right terminology. Could someone fill me in on that too? Thanks.

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  • How to automatically generate html table from image in Linux?

    - by alfish
    In Photoshop, you can easily devide the image into zones using point and click and it automatically generates the corresponding html with image slices addressed in tables. Gimp also has a Slice (Filter Web Slice) but it is so rudimentary and, as far as I can see, does not allow point and click selection of slices. I am wondering if the functionality can be added into Gimp, or there are other Linux software to do this. I hate to return to Windows jut to do this simple task which I happen to use frequently. Thanks in advance for your suggestions.

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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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  • Is there a table of OpenGL extensions, versions, and hardware support somewhere?

    - by Thomas
    I'm looking for some resource that can help me decide what OpenGL version my game needs at minimum, and what features to support through extensions. Ideally, a table of the following format: 1.0 1.1 1.2 1.2.1 1.3 ... multitexture - ARB ARB core core texture_float - EXT EXT ARB ARB ... (Not sure about the values I put in, but you get the idea.) The extension specs themselves, at opengl.org, list the minimum OpenGL version they need, so that part is easy. However, many extensions have been accepted and became core standard in subsequent OpenGL versions, but it is very hard to find when that happened. The only way I could find is to compare the full OpenGL standards document for each version. On a related note, I would also very much like to know which extensions/features are supported by which hardware, to help me decide what features I can safely use in my game, and which ones I need to make optional. For example, a big honkin' table like this: MAX_TEXTURE_IMAGE_UNITS MAX_VERTEX_TEXTURE_IMAGE_UNITS ... GeForce 6xxx 8 4 GeForce 7xxx 16 8 ATi x300 8 4 ... (Again, I'm making the values up.) The table could list hardware limitations from glGet but also support for particular extensions, and limitations of such extension support (e.g. what floating-point texture formats are supported in hardware). Any pointers to these or similar resources would be hugely appreciated!

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  • Alternative to NOT EXISTS

    - by Dave Colwell
    Hi all, I have two tables linked by an ID column, lets call them Table A and table B. My goal is to find all the records in table A that have no record in table B. For instance: Table A: ID----Value 1-----value1 2-----value2 3-----value3 4-----value4 Table B ID----Value 1-----x 2-----y 4-----z 4-----l As you can see, record with ID = 3 does not exist in table B, so i want a query that will give me record 3 from table A. the way i am currently doing this is by saying AND NOT EXISTS (SELECT ID FROM TableB) but since the tables are huge, the performance on this is terrible. Also, when i tried using a Left Join where TableB.ID is null, it didnt work. Can anyone suggest an alternative?

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  • Download LazyParser.NET

    - by Editor
    LazyParser.NET is a light-weight late-bound expression parser compatible with C# 2.0 expression syntax. It allows you to incorporate user-supplied mathematical expressions or any C# expression in your application which can be dynamically evaluated at runtime, using late binding. Any .NET class and/or method can be used in expressions, provided you allow access [...]

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  • [solved] Why can't I dynamically add lines to a HTML table using JavaScript in Internet Explorer?

    - by karlthorwald
    After many hours of debugging I am tired, maybe you can help me now to solve this: In a new Firefox it works, in my Internet Explorer 6 or 7 it doesn't: <html> <head> <script type="text/javascript"> function newLine() { var tdmod = document.createElement('td'); tdmod.appendChild(document.createTextNode("dynamic")); var tr = document.createElement('tr'); tr.appendChild(tdmod); var tt = document.getElementById("t1"); tt.appendChild(tr); } </script> </head> <body> <a href="#" onclick="newLine()">newLine</a> <table id="t1" border="1"> <tr> <td> static </td> </tr> </table> </body> You can klick on the link and new lines should be added to the table. Try it here: http://dl.dropbox.com/u/1508092/iejs.html#

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  • How do I use Ruby metaprogramming to refactor this common code?

    - by James Wenton
    I inherited a project with a lot of badly-written Rake tasks that I need to clean up a bit. Because the Rakefiles are enormous and often prone to bizarre nonsensical dependencies, I'm simplifying and isolating things a bit by refactoring everything to classes. Specifically, that pattern is the following: namespace :foobar do desc "Frozz the foobar." task :frozzify do unless Rake.application.lookup('_frozzify') require 'tasks/foobar' Foobar.new.frozzify end Rake.application['_frozzify'].invoke end # Above pattern repeats many times. end # Several namespaces, each with tasks that follow this pattern. In tasks/foobar.rb, I have something that looks like this: class Foobar def frozzify() # The real work happens here. end # ... Other tasks also in the :foobar namespace. end For me, this is great, because it allows me to separate the task dependencies from each other and to move them to another location entirely, and I've been able to drastically simplify things and isolate the dependencies. The Rakefile doesn't hit a require until you actually try to run a task. Previously this was causing serious issues because you couldn't even list the tasks without it blowing up. My problem is that I'm repeating this idiom very frequently. Notice the following patterns: For every namespace :xyz_abc, there is a corresponding class in tasks/... in the file tasks/[namespace].rb, with a class name that looks like XyzAbc. For every task in a particular namespace, there is an identically named method in the associated namespace class. For example, if namespace :foo_bar has a task :apples, you would expect to see def apples() ... inside the FooBar class, which itself is in tasks/foo_bar.rb. Every task :t defines a "meta-task" _t (that is, the task name prefixed with an underscore) which is used to do the actual work. I still want to be able to specify a desc-description for the tasks I define, and that will be different for each task. And, of course, I have a small number of tasks that don't follow the above pattern at all, so I'll be specifying those manually in my Rakefile. I'm sure that this can be refactored in some way so that I don't have to keep repeating the same idiom over and over, but I lack the experience to see how it could be done. Can someone give me an assist?

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  • Delegation, is this just opinionated or is there a common pattern?

    - by user1446714
    If I have a java class containing substantial code and I wish to add extra features, am I right in thinking the delegate class would have the additional features added as methods. Then my original class would create the delegate object and just call the extra functionality via the delegate instance? I am being told by somebody else that my original class should become the delegate and that the class containing the new functionality should contain an instance of the original class, to use as a delegate? This seemed a little backward to me, because there would be far more delegate calls because most of the code is now in the delegate.... I was always under the impression the delegate object would contain the additional new behaviour and an instance of it would be in the original class to inboke the new behaviour from?

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  • Is it necessary to mysql real escape when using alter table?

    - by cgwebprojects
    I noticed the other day that I cannot bind variables when using PDO with ALTER TABLE for example the following example will not work, $q = $dbc -> prepare("ALTER TABLE emblems ADD ? TINYINT(1) UNSIGNED NOT NULL DEFAULT '0', ADD ? DATETIME NOT NULL"); $q -> execute(array($emblemDB, $emblemDB . 'Date')); So is it necessary to use mysql_real_escape string and do it like below, // ESCAPE NAME FOR MYSQL INSERTION $emblemDB = mysql_real_escape_string($emblemDB); // INSERT EMBLEM DETAILS INTO DATABASE $q = $dbc -> prepare("ALTER TABLE emblems ADD " . $emblemDB . " TINYINT(1) UNSIGNED NOT NULL DEFAULT '0', ADD " . $emblemDB . "Date DATETIME NOT NULL"); $q -> execute(); Or do I not need to add in mysql_real_escape_string? As the only thing the query can do is ADD columns? Thanks

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  • Please suggest me the best way to design my database.

    - by Raymond Ho
    I have a table named "Pages" and a table named "Categories". Each entry of the table "Pages" is linked to the table "Categories". The "Categories" table have 5 entries, they are: "Car", "Websites", "Technology", "Mobile Phones", and "Interest". So each time I put an entry to the "Pages" table, I need to map it to the "Categories" table so are arranged properly. Here's my table: Pages ______ id [PK] name url Categories ______ id [PK] Categoryname Pages2Categories ______ Pages.id Categories.id So my question is, is this the most efficient way to create this kind of relationships between tables? It seems very amateur

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  • Why is SQLite3 using covering indices instead of the indices I created?

    - by Geoff
    I have an extremely large database (contacts has ~3 billion entries, people has ~280 million entries, and the other tables have a negligible number of entries). Most other queries I've run are really fast. However, I've encountered a more complicated query that's really slow. I'm wondering if there's any way to speed this up. First of all, here is my schema: CREATE TABLE activities (id INTEGER PRIMARY KEY, name TEXT NOT NULL); CREATE TABLE contacts ( id INTEGER PRIMARY KEY, person1_id INTEGER NOT NULL, person2_id INTEGER NOT NULL, duration REAL NOT NULL, -- hours activity_id INTEGER NOT NULL -- FOREIGN_KEY(person1_id) REFERENCES people(id), -- FOREIGN_KEY(person2_id) REFERENCES people(id) ); CREATE TABLE people ( id INTEGER PRIMARY KEY, state_id INTEGER NOT NULL, county_id INTEGER NOT NULL, age INTEGER NOT NULL, gender TEXT NOT NULL, -- M or F income INTEGER NOT NULL -- FOREIGN_KEY(state_id) REFERENCES states(id) ); CREATE TABLE states ( id INTEGER PRIMARY KEY, name TEXT NOT NULL, abbreviation TEXT NOT NULL ); CREATE INDEX activities_name_index on activities(name); CREATE INDEX contacts_activity_id_index on contacts(activity_id); CREATE INDEX contacts_duration_index on contacts(duration); CREATE INDEX contacts_person1_id_index on contacts(person1_id); CREATE INDEX contacts_person2_id_index on contacts(person2_id); CREATE INDEX people_age_index on people(age); CREATE INDEX people_county_id_index on people(county_id); CREATE INDEX people_gender_index on people(gender); CREATE INDEX people_income_index on people(income); CREATE INDEX people_state_id_index on people(state_id); CREATE INDEX states_abbreviation_index on states(abbreviation); CREATE INDEX states_name_index on states(name); Note that I've created an index on every column in the database. I don't care about the size of the database; speed is all I care about. Here's an example of a query that, as expected, runs almost instantly: SELECT count(*) FROM people, states WHERE people.state_id=states.id and states.abbreviation='IA'; Here's the troublesome query: SELECT * FROM contacts WHERE rowid IN (SELECT contacts.rowid FROM contacts, people, states WHERE contacts.person1_id=people.id AND people.state_id=states.id AND states.name='Kansas' INTERSECT SELECT contacts.rowid FROM contacts, people, states WHERE contacts.person2_id=people.id AND people.state_id=states.id AND states.name='Missouri'); Now, what I think would happen is that each subquery would use each relevant index I've created to speed this up. However, when I show the query plan, I see this: sqlite> EXPLAIN QUERY PLAN SELECT * FROM contacts WHERE rowid IN (SELECT contacts.rowid FROM contacts, people, states WHERE contacts.person1_id=people.id AND people.state_id=states.id AND states.name='Kansas' INTERSECT SELECT contacts.rowid FROM contacts, people, states WHERE contacts.person2_id=people.id AND people.state_id=states.id AND states.name='Missouri'); 0|0|0|SEARCH TABLE contacts USING INTEGER PRIMARY KEY (rowid=?) (~25 rows) 0|0|0|EXECUTE LIST SUBQUERY 1 2|0|2|SEARCH TABLE states USING COVERING INDEX states_name_index (name=?) (~1 rows) 2|1|1|SEARCH TABLE people USING COVERING INDEX people_state_id_index (state_id=?) (~5569556 rows) 2|2|0|SEARCH TABLE contacts USING COVERING INDEX contacts_person1_id_index (person1_id=?) (~12 rows) 3|0|2|SEARCH TABLE states USING COVERING INDEX states_name_index (name=?) (~1 rows) 3|1|1|SEARCH TABLE people USING COVERING INDEX people_state_id_index (state_id=?) (~5569556 rows) 3|2|0|SEARCH TABLE contacts USING COVERING INDEX contacts_person2_id_index (person2_id=?) (~12 rows) 1|0|0|COMPOUND SUBQUERIES 2 AND 3 USING TEMP B-TREE (INTERSECT) In fact, if I show the query plan for the first query I posted, I get this: sqlite> EXPLAIN QUERY PLAN SELECT count(*) FROM people, states WHERE people.state_id=states.id and states.abbreviation='IA'; 0|0|1|SEARCH TABLE states USING COVERING INDEX states_abbreviation_index (abbreviation=?) (~1 rows) 0|1|0|SEARCH TABLE people USING COVERING INDEX people_state_id_index (state_id=?) (~5569556 rows) Why is SQLite using covering indices instead of the indices I created? Shouldn't the search in the people table be able to happen in log(n) time given state_id which in turn is found in log(n) time?

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  • Data clean up: are there libraries of common permutations that we can use? Or is there a better appr

    - by anyaelena
    We are working on clean-up and analysis of a lot of human-entered customer data. We need to decide programmatically whether 2 addresses (for example) are the same, even though the data was entered with slight variations. Right now we run each address through fairly simplistic string replacement (replacing avenue with ave, for example), concatenate the fields and compare the results. We are doing something similar with names. At the very least, it seems like our list of search-replace values should already exist somewhere. Or perhaps you can suggest a totally different and superior way to detect matches?

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