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• Oracle Unique Indexes

  - by Melvin

  I was creating a new table today in 10g when I noticed an interesting behavior. Here is an example of what I did: CREATE TABLE test_table ( field_1 INTEGER PRIMARY KEY ); Oracle will by default, create a non-null unique index for the primary key. I double checked this. After a quick check, I find a unique index name SYS_C0065645. Everything…

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• Creating a foreign key in MySQL produces error:

  - by SnOrfus

  I'm trying to create a foreign key on a table in MySQL and I'm getting a strange error that there seems to be little info about in any of my searches. I'm creating the key with this (emitted from mysql workbench 5.2): ALTER TABLE `db`.`appointment` ADD CONSTRAINT `FK_appointment_CancellationID` FOREIGN KEY (`CancellationID` ) REFERENCES…

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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…

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• Working with foreign keys - cannot insert

  - by Industrial

  Hi everyone! Doing my first tryouts with foreign keys in a mySQL database and are trying to do a insert, that fails for this reason: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails Does this mean that foreign keys restrict INSERTS as well as DELETES and/or UPDATES on each table that is…

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• DataMapper: using auto_migrate! with many-to-many dependencies?

  - by pschuegr

  Hi, I'm trying to migrate my app from MySql to Postgresql, using Rails3-pre and the latest DataMapper. I have several models which are related through many-to-many relationships using :through = Resource, which means that DataMapper creates a join table with foreign keys for both models. I can't auto_migrate! these changes, because I…

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• Check if row already exists, if so tell the referenced table the id

  - by flhe

  Let's assume I have a table magazine: CREATE TABLE magazine ( magazine_id integer NOT NULL DEFAULT nextval(('public.magazine_magazine_id_seq'::text)::regclass), longname character varying(1000), shortname character varying(200), issn character varying(9), CONSTRAINT pk_magazine PRIMARY KEY (magazine_id) ); And another table…

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• Having difficulty catching postgresql exception in sequel/ruby

  - by mhd

  I have postgresql table that has somekind of unique constraint. I have ruby script that will update this table. The ruby script should be able to switch to UPDATE instead of INSERT when this kind of error occured: PGError: ERROR: duplicate key value violates unique constraint CMIIW, sequel seems cannot catch this exception?? …

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• Incorrect value for UNIQUE_CONSTRAINT_NAME in REFERENTIAL_CONSTRAINTS

  - by van

  I am listing all FK constraints for a given table using INFORMATION_SCHEMA set of views with the following query: SELECT X.UNIQUE_CONSTRAINT_NAME, "C".*, "X".* FROM "INFORMATION_SCHEMA"."KEY_COLUMN_USAGE" AS "C" INNER JOIN "INFORMATION_SCHEMA"."REFERENTIAL_CONSTRAINTS" AS "X" ON …

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• Django - Expression based model constraints

  - by rtmie

  Is it possible to set an expression based constraint on a django model object, e.g. If I want to impose a constraint where an owner can have only one widget of a given type that is not in an expired state, but can have as many others as long as they are expired. Obviously I can do this by overriding the save…

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• Why can I create a table with PRIMARY KEY on a nullable column?

  - by AlexKuznetsov

  The following code creates a table without raising any errors: CREATE TABLE test( ID INTEGER NULL, CONSTRAINT PK_test PRIMARY KEY(ID) ) Note that I cannot insert a NULL, as expected: INSERT INTO test VALUES(1),(NULL) ERROR: null value in column "id" violates not-null constraint DETAIL: Failing row…

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• ManyToManyField error when having recursive structure. How to solve it?

  - by luc

  Hello, I have the following table in the model with a recursive structure (a page can have children pages) class DynamicPage(models.Model): name = models.CharField("Titre",max_length=200) parent = models.ForeignKey('self',null=True,blank=True) I want to create another table with…

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• SQL SERVER – Enumerations in Relational Database – Best Practice

  - by pinaldave

  Marko Parkkola This article has been submitted by Marko Parkkola, Data systems designer at Saarionen Oy, Finland. Marko is excellent developer and always thinking at next level. You can read his earlier comment which created very interesting discussion here: SQL SERVER- IF EXISTS(Select null from…

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• HTML5 Form Validation

  - by Stephen.Walther

  The latest versions of Google Chrome (16+), Mozilla Firefox (8+), and Internet Explorer (10+) all support HTML5 client-side validation. It is time to take HTML5 validation seriously. The purpose of the blog post is to describe how you can take advantage of HTML5 client-side validation regardless…

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• Hello Operator, My Switch Is Bored

  - by Paul White

  This is a post for T-SQL Tuesday #43 hosted by my good friend Rob Farley. The topic this month is Plan Operators. I haven’t taken part in T-SQL Tuesday before, but I do like to write about execution plans, so this seemed like a good time to start. This post is in two parts. The first part is…

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• HTML5 Form Validation

  - by Stephen.Walther

  The latest versions of Google Chrome (16+), Mozilla Firefox (8+), and Internet Explorer (10+) all support HTML5 client-side validation. It is time to take HTML5 validation seriously. The purpose of the blog post is to describe how you can take advantage of HTML5 client-side validation…

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• Determining Merge Errors in a Typed DataSet

  Discover the underlying cause of Merge Constraint errors when merging DataSets.

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• Typical Applications of Linear System Solver in Game Developemnt

  - by craftsman.don

  I am going to write a custom solver for linear system. I would like to survey the typical problems involved the linear system solving in games. So that I can custom optimization on these problems based on the shape of the matrix. currently I am focus on these problems: B-Spline…

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• Project Euler 1: (Iron)Python

  - by Ben Griswold

  In my attempt to learn (Iron)Python out in the open, here’s my solution for Project Euler Problem 1.  As always, any feedback is welcome. # Euler 1 # http://projecteuler.net/index.php?section=problems&amp;id=1 # If we list all the natural numbers below 10 that…

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• Breaking 1NF to model subset constraints. Does this sound sane?

  - by Chris Travers

  My first question here. Appologize if it is in the wrong forum but this seems pretty conceptual. I am looking at doing something that goes against conventional wisdom and want to get some feedback as to whether this is totally insane or will result in problems, so critique…

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• Is it ok to initialize an RB_ConstraintActor in PostBeginPlay?

  - by Almo

  I have a KActorSpawnable subclass that acts weird. In PostBeginPlay, I initialize an RB_ConstraintActor; the default is not to allow rotation. If I create one in the editor, it's fine, and won't rotate. If I spawn one, it rotates. Here's the class: class QuadForceKActor…

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• How to verify the Liskov substitution principle in an inheritance hierarchy?

  - by Songo

  Inspired by this answer: Liskov Substitution Principle requires that Preconditions cannot be strengthened in a subtype. Postconditions cannot be weakened in a subtype. Invariants of the supertype must be preserved in a subtype. History constraint…

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• What data-structure/algorithm will allow me to send a list of key/value dictionaries using the least amount of bits?

  - by user12365

  I have server objects that have corresponding client objects. The data to be kept in sync is inside the server object's key/value dictionary. To keep the client objects in sync with the sever objects, I want the server to send the key/value dictionary every frame for…

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• referencing part of the composite primary key

  - by Zavael

  I have problems with setting the reference on database table. I have following structure: CREATE TABLE club( id INTEGER NOT NULL, name_short VARCHAR(30), name_full VARCHAR(70) NOT NULL ); CREATE UNIQUE INDEX club_uix ON club(id); ALTER TABLE club ADD…

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• Error deploying Spring with JAX-WS application in Jboss 6 server

  - by arlahiru

  I'm getting this error when I deploying spring+JAX-WS application in jboss server 6.1.0. 09:14:38,175 ERROR [org.springframework.web.context.ContextLoader] Context initialization failed: org.springframework.beans.factory.BeanCreationException: Error creating…

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• How to change the primary key to be non-clustered?

  - by AngryHacker

  Part-time reluctant DBA here. I want to change an existing primary key index from clustered to non-clustered. And the syntax is escaping me. This is how it's scripted out right now. ALTER TABLE [dbo].[Config] WITH NOCHECK ADD CONSTRAINT [PK_Config]…

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