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  • Database design - How can I have a foreign key of the primary key in the same table?

    - by Sergio Tapia
    My database has to store all the available departments in my company. Some departments are sub-departments on another existing department. I've decided to solve this like this: Departments ID Description HeadOfDepartment ParentDepartment ParentDepartment can be null, indicating it is a root department. If it has a parent I'll act accordingly, my question is how can I code this in Microsoft SQL?

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  • Add foreign key constraints to existing tables in Ruby on Rails (MySQL)

    - by randombits
    What's the best way to add foreign keys to my existing tables in Rails with an underlying MySQL database? clearly the solution should be done in a migration, as I want this versioned. Otherwise I'd create the constraints myself. I can't seem to find one, conducive response to they above. Again, the tables have already been created with previous migrations. I'm just going back now and adding referential integrity wherever it's applicable.

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  • Hashtable with int array as key in java

    - by Niels Hansen
    Hey! I'm trying to make a hashtable in java where the keys are int[], but it dosen't work. I have made a little test program to show my problem: public class test{ public static void main(String[] args){ int[] test0 = {1,1}; int[] test1 = {1,1}; Hashtable<int[], String> ht = new Hashtable<int[], String>(); String s0 = "foo"; ht.put(test0, s0); System.out.println("the result from ht.get(test1)"); System.out.println(ht.get(test1)); System.out.println("the result from ht.get(test0)"); System.out.println(ht.get(test0)); } } My intention is that both ht.get calles should return the same result, since the two arrays are equal, but they dont. Here is the result from running the code: the result from ht.get(test1) null the result from ht.get(test0) foo Am I missing something here or is it just impossible to use int[] as keys in a hastable?

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  • NHibernate and Composite Key References

    - by Rich
    I have a weird situation. I have three entities, Company, Employee, Plan and Participation (in retirement plan). Company PK: Company ID Plan PK: Company ID, Plan ID Employee PK: Company ID, SSN, Employee ID Participation PK: Company ID, SSN, Plan ID The problem is in linking the employee to the participation. From a DB perspective, participation should have Employee ID in the PK (it's not even in table). But it doesn't. NHibernate won't let me map the "has many" because the link expects 3 columns (since Employee PK has 3 columns), but I'd only provide 2. Any ideas on how to do this?

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  • Reading PGP key information

    - by calccrypto
    can someone show a description of the information of what a pgp looks like if only the descriptions were there but not the actual information? something like (i dont remember if the values are correct): packet-type[4 bits], total length in bytes[16 bits], packet version type [4 bits], creation-time[32 bits], encryption-algorithm[8 bits], ...,etc,etc ive tried to understand rfc4880, but its tedious and confusing. so far, i am think i have extracted the 4 i wrote above, but i cant seem to get the rest of the information out. can anyone help? i know i can just find some pgp program, but the whole point of this is to allow me to learn how those programs work in the first place

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  • Vertically Merge Multiple Tables in MySQL by Joint Primary Key

    - by world
    Hello, I'll attempt to make my question as clear as possible. I'm fairly unexperienced with SQL, only know the really basic queries. In order to have a better idea I'd been reading the MySQL manual for the past few days, but I couldn't really find a concrete solution and my needs are quite specific. I've got 3 MySQL MyISAM tables: table1, table2 and table3. Each table has an ID column (ID, ID2, ID3 respectively), and different data columns. For example table1 has [ID, Name, Birthday, Status, ...] columns, table2 has [ID2, Country, Zip, ...], table3 has [ID3, Source, Phone, ...] you get the idea. The ID, ID2, ID3 columns are common to all three tables... if there's an ID value in table1 it will also appear in table2 and table3. The number of rows in these tables is identical, about 10m rows in each table. What I'd like to do is create a new table that contains (most of) the columns of all three tables and merge them into it. The dates, for instance, must be converted because right now they're in VARCHAR YYYYMMDD format. Reading the MySQL manual I figured STR_TO_DATE() would do the job, but I don't know how to write the query itself in the first place so I have no idea how to integrate the date conversion. So basically, after I create the new table (which I do know how to do), how can I merge the three tables into it, integrating into the query the date conversion?

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  • Removing duplicate SQL records to permit a unique key

    - by j pimmel
    I have a table ('sales') in a MYSQL DB which should have rightfully have had a unique constraint enforced to prevent duplicates. To first remove the dupes and set the constraint is proving a bit tricky. Table structure (simplified): 'id (unique, autoinc)' product_id The goal is to enforce uniqueness for product_id. The de-duping policy I want to apply is to remove all duplicate records except the most recently created, eg: the highest id Or to put another way, I would like to delete duplicate records, excluding the ids matched by the following query: select id from sales s inner join (select product_id, max(id) as maxId from sales group by product_id having count(product_id) > 1) groupedByProdId on s.product_id and s.id = groupedByProdId.maxId I've struggled with this on two fronts - writing the query to select the correct records to delete and then also the constraint in MYSQL where a subselect FROM clause of a DELETE cannot reference the same table from which data is being removed.

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  • Can I use foreign key restrictions to return meaningful UI errors with PHP

    - by Shane
    I want to start by saying that I am a big fan of using foreign keys and have a tendency to use them even on small projects to keep my database from being filled with orphaned data. On larger projects I end up with gobs of keys which end up covering upwards of 8 - 10 layers of data. I want to know if anyone could suggest a graceful way of handling 'expected errors' from the MySQL database in a way that I can construct meaningful messages for the end user. I will explain 'expected errors' with an example. Lets say I have a set of tables used for basic discussions: discussion questions responses users Hierarchically they would probably look something like this: -users --discussion ---questions ----responses When I attempt to delete a user the FKs will check discussions and if any discussion exist the deletion is restricted, deleting discussion checks questions, deleting questions checks responses. An 'expected error' in this case would be attempting to delete a user--unless they are newly created I can anticipate that one or more foreign keys will fail causing an error. What I WANT to do is to catch that error on deletion and be able to tell the end user something like 'We're sorry, but all discussions must be removed before you can delete this user...'. Now I know I can keep and maintain matching arrays in PHP and map specific errors to messages but that is messy and prone to becoming stagnant, or I could manually run a set of selects prior to attempting the deletion, but then I am doing just as much work as without using FKs. Any help here would be greatly appreciated, or if I am just looking at this completely wrong then please let me know. On a side note I generally use CodeIgniter for my application development, so if that would open up an avenue through that framework please consider that in your answers. Thanks in Advance

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  • Djangoo Foreign key queries

    - by Hulk
    In the following model: class header(models.Model): title = models.CharField(max_length = 255) created_by = models.CharField(max_length = 255) def __unicode__(self): return self.id() class criteria(models.Model): details = models.CharField(max_length = 255) headerid = models.ForeignKey(header) def __unicode__(self): return self.id() class options(models.Model): opt_details = models.CharField(max_length = 255) headerid = models.ForeignKey(header) def __unicode__(self): return self.id() If there is a row in the database for table header as Id=1, title=value-mart , createdby=CEO How do i query criteria and options tables to get all the values related to header table id=1 Also can some one please suggest a good link for queries examples, Thanks..

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  • Guid Primary /Foreign Key dilemma SQL Server

    - by Xience
    Hi guys, I am faced with the dilemma of changing my primary keys from int identities to Guid. I'll put my problem straight up. It's a typical Retail management app, with POS and back office functionality. Has about 100 tables. The database synchronizes with other databases and receives/ sends new data. Most tables don't have frequent inserts, updates or select statements executing on them. However, some do have frequent inserts and selects on them, eg. products and orders tables. Some tables have upto 4 foreign keys in them. If i changed my primary keys from 'int' to 'Guid', would there be a performance issue when inserting or querying data from tables that have many foreign keys. I know people have said that indexes will be fragmented and 16 bytes is an issue. Space wouldn't be an issue in my case and apparently index fragmentation can also be taken care of using 'NEWSEQUENTIALID()' function. Can someone tell me, from there experience, if Guid will be problematic in tables with many foreign keys. I'll be much appreciative of your thoughts on it...

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  • RAW key generation in IOS with AES

    - by sudheer
    I am novice to the cryptography in ios . I got a requirement to convert android encryption code into IOS . Below is the android code part. I need that in IOS . Can any one please help me out in this . I need this below android code in IOS. private static byte[] getRawKey(byte[] seed) throws Exception { KeyGenerator kgen = KeyGenerator.getInstance("AES"); SecureRandom sr = SecureRandom.getInstance("SHA1PRNG"); sr.setSeed(seed); kgen.init(256, sr); SecretKey skey = kgen.generateKey(); byte[] raw = skey.getEncoded(); return raw; }

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  • Where clause on joined table used for user defined key/value pairs

    - by Steve Wright
    Our application allows administrators to add “User Properties” in order for them to be able to tailor the system to match their own HR systems. For example, if your company has departments, you can define “Departments” in the Properties table and then add values that correspond to “Departments” such as “Jewelry”, “Electronics” etc… You are then able to assign a department to users. Here is the schema: In this schema, a User can have only one UserPropertyValue per Property, but doesn’t have to have a value for the property. I am trying to build a query that will be used in SSRS 2005 and also have it use the PropertyValues as the filter for users. My query looks like this: SELECT UserLogin, FirstName, LastName FROM Users U LEFT OUTER JOIN UserPropertyValues UPV ON U.ID = UPV.UserID WHERE UPV.PropertyValueID IN (1, 5) When I run this, if the user has ANY of the property values, they are returned. What I would like to have is where this query will return users that have values BY PROPERTY. So if PropertyValueID = 1 is of Department (Jewelry), and PropertyValueID = 5 is of EmploymentType (Full Time), I want to return all users that are in Department Jewelry that are EmployeeType of Full Time, can this be done? Here's a full data example: User A has Department(Jewelry value = 1) and EmploymentType(FullTime value = 5)User B has Department(Electronics value = 2) and EmploymentType(FullTime value = 5)User C has Department(Jewelry value = 1) and EmployementType(PartTime value = 6) My query should only return User A using the above query UPDATE: I should state that this query is used as a dataset in SSRS, so the parameter passed to the query will be @PropertyIDs and it is defined as a multi-value parameter in SSRS. WHERE UPV.PropertyValueID IN (@PropertyIDs)

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  • C# Reading the registry and Wow6432Node key

    - by Jade M
    Hi all, I have come code that reads the registry and looks for a value in HKEY_LOCAL_MACHINE\Software\App\ but when running on 64bit versions of Windows the value is under HKEY_LOCAL_MACHINE\Software\Wow6432Node\App. How should I best approach this? Do I need a 64bit installer or should I rewrite my code to detect both places? Thanks

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  • UIView as dictionary key?

    - by subw
    I want to have a NSDictionary that maps from UIViews to something else. However, since UIViews do not implement the NSCopying protocol, I can't use them directly as dictionary keys.

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  • Django dictionary in templates: Grab key from another objects attribute

    - by Jordan Messina
    I have a dictionary called number_devices I'm passing to a template, the dictionary keys are the ids of a list of objects I'm also passing to the template (called implementations). I'm iterating over the list of objects and then trying to use the object.id to get a value out of the dict like so: {% for implementation in implementations %} {{ number_devices.implementation.id }} {% endfor %} Unfortunately number_devices.implementation is evaluated first, then the result.id is evaluated obviously returning and displaying nothing. I can't use parentheses like: {{ number_devices.(implementation.id) }} because I get a parse error. How do I get around this annoyance in Django templates? Thanks for any help!

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  • PHP Array Key & value Question

    - by Nano HE
    Hi I writed a test code as below. <?php $url = 'http://localhost/events/result/cn_index.php?login'; print_r(parse_url($url)); echo parse_url($url, PHP_URL_PATH); ?> Output Array ( [scheme] => http [host] => localhost [path] => /events/result/cn_index.php [query] => login ) /events/result/cn_index.php Now I inserted the line below echo array[query]; // I want to echo 'login', but failed. How to the the value of 'login'?

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  • Entity Framework autoincrement key

    - by Tommy Ong
    I'm facing an issue of duplicated incremental field on a concurrency scenario. I'm using EF as the ORM tool, attempting to insert an entity with a field that acts as a incremental INT field. Basically this field is called "SequenceNumber", where each new record before insert, will read the database using MAX to get the last SequenceNumber, append +1 to it, and saves the changes. Between the getting of last SequenceNumber and Saving, that's where the concurrency is happening. I'm not using ID for SequenceNumber as it is not a unique constraint, and may reset on certain conditions such as monthly, yearly, etc. InvoiceNumber | SequenceNumber | DateCreated INV00001_08_14 | 1 | 25/08/2014 INV00001_08_14 | 1 | 25/08/2014 <= (concurrency is creating two SeqNo 1) INV00002_08_14 | 2 | 25/08/2014 INV00003_08_14 | 3 | 26/08/2014 INV00004_08_14 | 4 | 27/08/2014 INV00005_08_14 | 5 | 29/08/2014 INV00001_09_14 | 1 | 01/09/2014 <= (sequence number reset) Invoice number is formatted based on the SequenceNumber. After some research I've ended up with these possible solutions, but wanna know the best practice 1) Optimistic Concurrency, locking the table from any reads until the current transaction is completed (not fancy of this idea as I guess performance will be of a great impact?) 2) Create a Stored Procedure solely for this purpose, does select and insert on a single statement as such concurrency is at minimum (would prefer a EF based approach if possible)

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  • Simple App Engine Sessions Implementation

    - by raz0r
    Here is a very basic class for handling sessions on App Engine: """Lightweight implementation of cookie-based sessions for Google App Engine. Classes: Session """ import os import random import Cookie from google.appengine.api import memcache _COOKIE_NAME = 'app-sid' _COOKIE_PATH = '/' _SESSION_EXPIRE_TIME = 180 * 60 class Session(object): """Cookie-based session implementation using Memcached.""" def __init__(self): self.sid = None self.key = None self.session = None cookie_str = os.environ.get('HTTP_COOKIE', '') self.cookie = Cookie.SimpleCookie() self.cookie.load(cookie_str) if self.cookie.get(_COOKIE_NAME): self.sid = self.cookie[_COOKIE_NAME].value self.key = 'session-' + self.sid self.session = memcache.get(self.key) if self.session: self._update_memcache() else: self.sid = str(random.random())[5:] + str(random.random())[5:] self.key = 'session-' + self.sid self.session = dict() memcache.add(self.key, self.session, _SESSION_EXPIRE_TIME) self.cookie[_COOKIE_NAME] = self.sid self.cookie[_COOKIE_NAME]['path'] = _COOKIE_PATH print self.cookie def __len__(self): return len(self.session) def __getitem__(self, key): if key in self.session: return self.session[key] raise KeyError(str(key)) def __setitem__(self, key, value): self.session[key] = value self._update_memcache() def __delitem__(self, key): if key in self.session: del self.session[key] self._update_memcache() return None raise KeyError(str(key)) def __contains__(self, item): try: i = self.__getitem__(item) except KeyError: return False return True def _update_memcache(self): memcache.replace(self.key, self.session, _SESSION_EXPIRE_TIME) I would like some advices on how to improve the code for better security. Note: In the production version it will also save a copy of the session in the datastore. Note': I know there are much more complete implementations available online though I would like to learn more about this subject so please don't answer the question with "use that" or "use the other" library.

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  • avoid duplication with auto increment key in Hibernate

    - by Lily
    I am trying to use Hibernate to auto increment the id, however, I try to avoid duplication. class Service { Long id; // auto increment String name; String owner; // setter and getter } What I want to achieve is, whenever name and owner are the same, it will be a duplicated entry. In this case, I don't want to add another entry into the Database anymore. How to revise the hbm.xml files to avoid this issue?

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  • Fluent NHibernate - How to map the foreign key column as a property

    - by Steve
    I am sure this is a straightforward question but consider the following: I have a reference between company and sector as follows: public class Company { public Guid ID { get; set; } public Sector Sector { get; set; } public Guid SectorID { get; set; } } public class Sector { public Guid ID { get; set; } public string Name { get; set; } } Ok. What I want is the SectorID of the Company object to be populated after I go: (new Company()).Sector = new Sector() { Name="asdf" } and do a flush. The mapping I am using kindly creates an additional column in the database called Sector_Id in the Company table, but this is not available as a property on Company. I want the SectorID property to be filled. The mapping i am currently using in the CompanyMap is References(c = c.Sector).Cascade.All(); Does anyone have any ideas?

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  • Sql Server problems reading columns with a foreigh key

    - by illdev
    I have a weird situation, where simple queries seem to never finish for instance SELECT top 100 ArticleID FROM Article WHERE ProductGroupID=379114 returns immediately SELECT top 1000 ArticleID FROM Article WHERE ProductGroupID=379114 never returns SELECT ArticleID FROM Article WHERE ProductGroupID=379114 never returns SELECT top 1000 ArticleID FROM Article returns immediately by 'returning' I mean 'in query analyzer the green check mark appears and it says "Query executed successfully"'. I sometimes get the rows painted to the grid in qa, but still the query goes on waiting for my client to time out - 'sometimes': SELECT ProductGroupID AS Product23_1_, ArticleID AS ArticleID1_, ArticleID AS ArticleID18_0_, Inventory_Name AS Inventory3_18_0_, Inventory_UnitOfMeasure AS Inventory4_18_0_, BusinessKey AS Business5_18_0_, Name AS Name18_0_, ServesPeople AS ServesPe7_18_0_, InStock AS InStock18_0_, Description AS Descript9_18_0_, Description2 AS Descrip10_18_0_, TechnicalData AS Technic11_18_0_, IsDiscontinued AS IsDisco12_18_0_, Release AS Release18_0_, Classifications AS Classif14_18_0_, DistributorName AS Distrib15_18_0_, DistributorProductCode AS Distrib16_18_0_, Options AS Options18_0_, IsPromoted AS IsPromoted18_0_, IsBulkyFreight AS IsBulky19_18_0_, IsBackOrderOnly AS IsBackO20_18_0_, Price AS Price18_0_, Weight AS Weight18_0_, ProductGroupID AS Product23_18_0_, ConversationID AS Convers24_18_0_, DistributorID AS Distrib25_18_0_, type AS Type18_0_ FROM Article AS articles0_ WHERE (IsDiscontinued = '0') AND (ProductGroupID = 379121) shows this behavior. I have no idea what is going on. Probably select is broken ;) Anyone can tell me how to handle such a situation? More info, anyone?

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  • switching default keyevents actions after key combinations

    - by liysd
    I need to change default actions of two events. When I press "enter" one action occurs, when I press "shift-enter" another. I need to switch it. I means if I press "enter" than "shift-enter" action occurs. I tried something like this but if doesn't work. f(evt.keyCode == 13) { if(!evt.shiftKey){ evt.preventDefault(); evt.shiftKey = true; var e = jQuery.Event("keydown"); e.which = 13; e.shiftKey = true; $(wym._doc).trigger(e); Is there any way to do it?

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