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• What are the repercussions of not checking existing data when adding a foreign key?

  - by scottm

  I've inherited a database that doesn't exactly strive for data integrity. I am trying to add some foreign keys to change that, but there is data in some tables that doesn't fit the constraints. Most likely, the data won't be used again so I want to know what problems I might face by leaving it there. The other option I see is to move it into some kind of table without referential constraints, just for historical purposes. So, what are the repercussions of not checking existing data? If I create a foreign key constraint on a table and don't check existing data, will all new data inserted into the table be enforced?

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• How to implement a book preview (2 page spread) without using Flash?

  - by littlejim84

  I'm looking into a solution for work, where you have a two page spread of the book to preview. Either side of this, you can hover in the corner to create a pseudo-flip and then click the mouse button to actually turn the page. I know there is many Flash solutions out there, but in this case we cannot use it... So we are looking for a possible solution that can work across all major browsers (yes, including IE6)... I looked a few canvas solutions, but with Google's canvas extension for IE, these will terribly slow. So was thinking about an SVG/VML solution, like Raphael Javascript library. This could be good, but then trying to look into how to code this, without examples, could be a challenge with the time constraint. Is there a solution out there that fits (or almost fits) this problem?

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• Oracle: TABLE ACCESS FULL with Primary key?

  - by tim

  There is a table: CREATE TABLE temp ( IDR decimal(9) NOT NULL, IDS decimal(9) NOT NULL, DT date NOT NULL, VAL decimal(10) NOT NULL, AFFID decimal(9), CONSTRAINT PKtemp PRIMARY KEY (IDR,IDS,DT) ) ; SQL>explain plan for select * from temp; Explained. SQL> select plan_table_output from table(dbms_xplan.display('plan_table',null,'serial')); PLAN_TABLE_OUTPUT -------------------------------------------------------------------------------- --------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| --------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | 61 | 2 (0)| | 1 | TABLE ACCESS FULL| TEMP | 1 | 61 | 2 (0)| --------------------------------------------------------------- Note ----- - 'PLAN_TABLE' is old version 11 rows selected. SQL server 2008 shows in the same situation Clustered index scan. What is the reason?

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• Stuck on solving the Minimal Spanning Tree problem.

  - by kunjaan

  I have reduced my problem to finding the minimal spanning tree in the graph. But I want to have one more constraint which is that the total degree for each vertex shouldnt exceed a certain constant factor. How do I model my problem? Is MST the wrong path? Do you know any algorithms that will help me? One more problem: My graph has duplicate edge weights so is there a way to count the number of unique MSTs? Are there algorithms that do this? Thank You. Edit: By degree, I mean the total number of edges connecting the vertex. By duplicate edge weight I mean that two edges have the same weight.

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• deleting a large number of rows from a table

  - by Azeem

  We have a requirement to delete rows in the order of millions from multiple tables as a batch job (note that we are not deleting all the rows, we are deleting based on a timestamp stored in an indexed column). Obviously a normal DELETE takes forever (because of logging, referential constraint checking etc.). I know in the LUW world, we have ALTER TABLE NOT LOGGED INITIALLY but I can't seem to find the an equivalent SQL statement for DB2 v8 z/OS. Any one has any ideas on how to do this really fast? Also, any ideas on how to avoid the referential checks when deleting the rows? Please let me know.

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• SQL Server 2000, how to automate import data from excel

  - by Stan

  Say the source data comes in excel format, below is how I import the data. Converting to csv format via MS Excel Roughly find bad rows/columns by inspecting backup the table that needs to be updated in SQL Query Analyzer truncate the table (may need to drop foreign key constraint as well) import data from the revised csv file in SQL Server Enterprise Manager If there's an error like duplicate columns, I need to check the original csv and remove them I was wondering how to make this procedure more effecient in every step? I have some idea but not complete. For step 2&6, using scripts that can check automatically and print out all error row/column data. So it's easier to remove all errors once. For step 3&5, is there any way to automatically update the table without manually go through the importing steps? Could the community advise, please? Thanks.

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• Behaviour to simulate an enum implementing an interface

  - by fearofawhackplanet

  Say I have an enum something like: enum OrderStatus { AwaitingAuthorization, InProduction, AwaitingDespatch } I've also created an extension method on my enum to tidy up the displayed values in the UI, so I have something like: public static string ToDisplayString(this OrderStatus status) { switch (status) { case Status.AwaitingAuthorization: return "Awaiting Authorization"; case Status.InProduction: return "Item in Production"; ... etc } } Inspired by the excellent post here, I want to bind my enums to a SelectList with an extension method: public static SelectList ToSelectList<TEnum>(this TEnum enumObj) however, to use the DisplayString values in the UI drop down I'd need to add a constraint along the lines of : where TEnum has extension ToDisplayString Obviously none of this is going to work at all with the current approach, unless there's some clever trick I don't know about. Does anyone have any ideas about how I might be able to implement something like this?

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• Truncating a table referenced by a foreign key

  - by born to hula

  Hey, We have two tables in a SQL Server 2005 database, A and B.There is a service which truncates table A every day. Recently, a foreign key constraint was added to table B, referencing table A. As a result, it isn't possible truncating table A anymore, even if table B is empty. Is there any workaround to get the same result as truncating table A? I've already tried the approach below but the identity wasn't reset. DBCC CHECKIDENT (TABLENAME, RESEED, 0) PS. before anyone points this as a duplicate, the different thing here is that I'm not allowed to drop constraints, nor creating any.

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• Save or update for FK relationship Sqlalchemy

  - by Alex

  I've googled, but haven't been able to find the answer to this seemingly simple question. I have two relations, a customer and an order. Each order is associated to a single cusomter, and therefore has a FK relationship to the customer table. The customer relation only stores customer names, and I have set a unique constraint on the customer table barring duplicate names. Let's say I create a new order instance and set a customer for the order. Something like: order_instance.customer = Customer("customer name") When I save the order instance, SqlAlchemy will complain if a customer with this name already exists in the customer table. How do I specify to SqlAlchemy to insert into the customer table if a customer with this name doesn't already exist, or just ignore (or even update) to the customer relation? I don't really want to have to check each time if a customer with some name already exists...

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• SQL Server Composite Primary Keys

  - by Colin

  I am attempting to replace all records for a give day in a certain table. The table has a composite primary key comprised of 7 fields. One such field is date. I have deleted all records which have a date value of 2/8/2010. When I try to then insert records into the table for 2/8/2010, I get a primary key violation. The records I am attempting to insert are only for 2/8/2010. Since date is a component of the PK, shouldn't there be no way to violate the constraint as long as the date I'm inserting is not already in the table? Thanks in advance.

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• Interpreting type codes in sys.objects in SQL Server

  - by fatcat1111

  On SQL Server, the sys.objects table includes "Type" and "Type_Desc" attributes. For example: SELECT DISTINCT [Type], Type_Desc FROM Sys.Objects ORDER BY [Type] Returns: C CHECK_CONSTRAINT D DEFAULT_CONSTRAINT F FOREIGN_KEY_CONSTRAINT FN SQL_SCALAR_FUNCTION FS CLR_SCALAR_FUNCTION IT INTERNAL_TABLE P SQL_STORED_PROCEDURE PK PRIMARY_KEY_CONSTRAINT S SYSTEM_TABLE SQ SERVICE_QUEUE TR SQL_TRIGGER U USER_TABLE UQ UNIQUE_CONSTRAINT V VIEW Is there a comprehensive list of these types somewhere? There isn't a constraint on sys.objects that points me to table of these, and sys.types contains data types. I've searched SQL BOL but haven't found it. Any help would be appreciated. EDIT: Some DBs use only a subset of these types. For example, if I have a database with no views, when I query Sys.Objects as above, there are no "V" rows in the results. I am looking for a list of all possible types and descriptions used by SQL Server.

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• Nesting a SharePoint Webpart inside of a User Control

  - by jlech

  I know it's usually the other way around, but I have some extenuating requirements that must be met (read as "No one bothered to do the research and now I have to bail them out") I have a standard user control (ascx) that is to be imported into a SharePoint 2007 website. Due to a design constraint, a sharepoint web part that is also needed has to be nested inside of this user control. So in other words, the user control would have to look something like this: <%@ Control Language="C#" AutoEventWireup="true" CodeFile="foo.ascx.cs" Inherits="foo" %> <div id="container"> ...snipped... <!-- SharePoint web part goes here --> ...snipped... </div> Any help would be appreciated. Thanks!

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• OpenERP model tracking external resource, hooking into parent's copy() or copy_data()

  - by CB.

  I have added a new model (call it crm_lead_external) that is linked via a new one2many on crm_lead. Thus, my module has two models defined: an updated crm_lead (with _name=crm_lead) and a new crm_lead_external. This external model tracks a file and as such has a 'filename' field. I also created a unique SQL index on this filename field. This is part of my module: def copy(self, cr, uid, id, default=None, context=None): if not default: default = {} default.update({ 'state': 'new', 'filename': '', }) ret = super(crm_lead_external, self).copy(cr, uid, id, default, context=context) #do file copy return ret The intent here is to allow an external entity to be duplicated, but to retarget the file path. Now, if I click duplicate on the Lead, I get an IntegrityError on my unique constraint. Is there a particular reason why copy() isn't being called? Should I add this logic to copy_data()? Myst I really override copy() for the lead? Thanks in advance.

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• Retrieve a cross domain RSS(xml) through Javascript

  - by Ajay

  I have seen server side proxy workarounds for retrieving rss (xmls) from cross-domains. In fact this very question addressess my same problem but gives out a different solution. I have a constraint of do not use a proxy to retrieve rss feeds. And hence the Google AJAX Feed API solution also goes out of picture. Is there a client-only workaround for this problem. JSONP is the solution for requests that respond with JSON output. But here, I have RSS feeds which can respond with pure xml . How do I solve the problem.

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• T-SQL Self Join in combination with aggregate function

  - by Nick

  Hi, i have the following table. CREATE TABLE [dbo].[Tree]( [AutoID] [int] IDENTITY(1,1) NOT NULL, [Category] [varchar](10) NULL, [Condition] [varchar](10) NULL, [Description] [varchar](50) NULL, CONSTRAINT [PK_Tree] PRIMARY KEY CLUSTERED ( [AutoID] 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 the data looks like this: INSERT INTO [Test].[dbo].[Tree] ([Category] ,[Condition] ,[Description]) VALUES ('1','Alpha','Type 1') INSERT INTO [Test].[dbo].[Tree] ([Category] ,[Condition] ,[Description]) VALUES ('1','Alpha','Type 1') INSERT INTO [Test].[dbo].[Tree] ([Category] ,[Condition] ,[Description]) VALUES ('2','Alpha','Type 2') INSERT INTO [Test].[dbo].[Tree] ([Category] ,[Condition] ,[Description]) VALUES ('2','Alpha','Type 2') go I try now to do the following: SELECT Category,COUNT(*) as CategoryCount FROM Tree where Condition = 'Alpha' group by Category but i wish also to get the Description for each Element. I tried several subqueries, self joins etc. i always come to the problem that the subquery cannot return more than one record. The problem is caused by a poor database design which i cannot change and i run out of ideas to get this done in a single query ;-(

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• receive a responseText in ajax but without div tag

  - by kawtousse

  Hi everyone I want to know if there is any other way whithout using a div tag to receive response html when sending parameter whith ajax. I'am asking because when iam building the select in other servlet and returning the result to jsp it receive the responsehtml in a div tag when we use the famous: x = xhr.responseText; document.getElementById('param').innerHTML = x; with param is the id of div tag. Note: this works fine when populating ddl but its constraint are multiple for my case. Thinks.

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• Change master table PK and update related table FK (changing PK from Autoincrement to UUID on Mysql)

  - by eleonzx

  I have two related tables: Groups and Clients. Clients belongs to Groups so I have a foreign key "group_id" that references the group a client belongs to. I'm changing the Group id from an autoincrement to a UUID. So what I need is to generate a UUID for each Group and update the Clients table at once to reflect the changes and keep the records related. Is there a way to do this with multiple-table update on MySQL? Adding tables definitions for clarification. CREATE TABLE `groups` ( `id` char(36) NOT NULL, `name` varchar(255) DEFAULT NULL, `created` datetime DEFAULT NULL, `modified` datetime DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8$$ CREATE TABLE `clients` ( `id` char(36) NOT NULL, `name` varchar(255) NOT NULL, `group_id` char(36) DEFAULT NULL, `active` tinyint(1) DEFAULT '1' PRIMARY KEY (`id`), KEY `fkgp` (`group_id`), CONSTRAINT `fkgp` FOREIGN KEY (`group_id`) REFERENCES `groups` (`id`) ON DELETE NO ACTION ON UPDATE CASCADE ) ENGINE=InnoDB DEFAULT CHARSET=utf8$$

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• Why repeat database constraints in models?

  - by BWelfel

  In a CakePHP application, for unique constraints that are accounted for in the database, what is the benefit of having the same validation checks in the model? I understand the benefit of having JS validation, but I believe this model validation makes an extra trip to the DB. I am 100% sure that certain validations are made in the DB so the model validation would simply be redundant. The only benefit I see is the app recognizing the mistake and adjusting the view for the user accordingly (repopulating the fields and showing error message on the appropriate field; bettering the ux) but this could be achieved if there was a constraint naming convention and so the app could understand what the problem was with the save (existing method to do this now?)

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• what are the various approaches for generating PDFs?

  - by andthereitgoes

  I have an idea for an app that would take some flash content which contains graphics and images like various geometric shapes and polygons and some random images and convert them to PDF. Also, since I envision this app to be used my multiple users I want this process to be quick and scalable. One possible solution I could think of is have a small flash client with the capability of assembling the above mentioned graphics and images. Generate some sort of XML, send it to a server running a Java process which could render the PDF using iText. I was wondering what are the other possible ways to do it or the best practices. Technology isn't an issue; open source or commercial. I am looking for ideas to make the process fast and scalable. Most importantly, I don't want the back end server side PDF render engine to constraint the flash client capabilities. I would appreciate if you could share your tech stack idea. Thanks a lot!

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• Multiple column foreign key contraints

  - by eugene4968

  I want to setup table constraints for the following scenario and I’m not sure how to do it or if it’s even possible in SQL Server 2005. I have three tables A,B,C. C is a child of B. B will have a optional foreign key(may be null) referencing A. For performance reasons I also want table C to have the same foreign key reference to table A. The constraint on table C should be that C must reference its parent (B) and also have the same foreign key reference to A as its parent. Anyone have any thoughts on how to do this?

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• Add Unique Key For Nullable Columns - SQL Server

  - by Ruby

  I'm using sql server 2008 R2 and would like to apply unique key constraint to nullable columns. This code works good, but if I have multiple columns to add this rule to, it would generate as many 'nullbuster' columns. ALTER TABLE tblBranch ADD nullbuster AS (CASE WHEN column1 IS NULL THEN BranchID ELSE NULL END); CREATE UNIQUE INDEX UK_Column1 ON tblBranch(column1,nullbuster); tblBranch is the table name, nullbuster would be the new column name, BranchId is the Primary key column of the target table, and Column1 is the column name of the target column. Is there any way that I could achieve the goal without generating new columns.

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• How to call javascript function when url variable is sent

  - by mattlarkin

  Hello, heres basically what I need to get done. I have a jsp page which allows me to add/modify/delete an item. The items are stored in a database which I have controller classes to access(dont worry bout that part) When an item gets selected and deleted the id of the item gets sent to the controller to be processed. The item will not always be deleted if their is a foreign key constraint so I send either a delete=true or delete=false through url back to the jsp page. I would like to have it so a javascript function gets called displaying an alert saying the item was deleted or the item was not deleted. can someone please tell me the best way to do this? thank you

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• MySQL Full-text Search Workaround for innoDB tables

  - by Rob

  I'm designing an internal web application that uses MySQL as its backend database. The integrity of the data is crucial, so I am using the innoDB engine for its foreign key constraint features. I want to do a full-text search of one type of records, and that is not supported natively with innoDB tables. I'm not willing to move to MyISAM tables due to their lack of foreign key support and due to the fact that their locking is per table, not per row. Would it be bad practice to create a mirrored table of the records I need to search using the MyISAM engine and use that for the full-text search? This way I'm just searching a copy of the data and if anything happens to that data it's not as big of a deal because it can always be re-created. Or is this an awkward way of doing this that should be avoided? Thanks.

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• Typeclass instances for unnamed types in Scala

  - by ncreep

  How would one encode the following constraint in Scala (pseudocode)? def foo(x: T forSome { type T has a Numeric[T] instance in scope }) = { val n= implicitly[...] // obtain the Numeric instance for x n.negate(x) // and use it with x } In words: I need a type class instance for my input argument, but I don't care about the argument's type, I just need to obtain the instance and use it on my argument. It doesn't have to be an existential type, but I need to avoid type parameters in the def's signature. Thanks.

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• Using Rails, how can I set my primary key to not be an integer-typed column?

  - by Rudd Zwolinski

  I'm using Rails migrations to manage a database schema, and I'm creating a simple table where I'd like to use a non-integer value as the primary key (in particular, a string). To abstract away from my problem, let's say there's a table employees where employees are identified by an alphanumeric string, e.g. "134SNW". I've tried creating the table in a migration like this: create_table :employees, {:primary_key => :emp_id} do |t| t.string :emp_id t.string :first_name t.string :last_name end What this gives me is what seems like it completely ignored the line t.string :emp_id and went ahead and made it an integer column. Is there some other way to have rails generate the PRIMARY_KEY constraint (I'm using PostgreSQL) for me, without having to write the SQL in an execute call? NOTE: I know it's not best to use string columns as primary keys, so please no answers just saying to add an integer primary key. I may add one anyway, but this question is still valid.

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