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  • Referencing surrogate key

    - by Arman
    I have a table that has an autoincrement surrogate key. I want to use it as a foreign key of my other table. The thing is, I cant figure out how I can reference it to that table, because it is nearly impossible to determine what I have to reference(the actual value of the surrogate key). Please be noted that what I am trying to do is adding a tuple/record through my program(outside the dbms). The process is: Add a new record in Table1 and generate an autoincrement key. Update Add a new record in Table2 and reference its foreign key to the primary key of Table1. Update My question is : HOW do I store the foreign key if I didnt know what is it?

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  • How to use multiple identity numbers in one table?

    - by vincer
    I have an web application that creates printable forms, these forms have a unique number on them, the problem is I have 2 forms that separate numbers need to be created for them. ie) Form1- Numbered 2000000-2999999 Form2- Numbered 3000000-3999999 dbo.test2 - is my form information table Tsel - is my autoinc table for the 3000000 series numbers Tadv - is my autoinc table for the 2000000 series numbers What I have done is create 2 tables with just autoinc row (one for 2000000 series numbers and one for 3000000 series numbers), I then created a trigger to add a record to the coresponding table, read back the autoinc number and add it to my table that stores the form information including the just created autoinc number for the right series of forms. Although it does work, I'm concerned that the numbers will get messed up under load. I'm not sure the @@IDENTITY will always return the right value when many people are using the system. (I cannot have duplicates and I need to use the numbering form show above. See code below. ** TRIGGER ** CREATE TRIGGER MAKEANID2 ON dbo.test2 AFTER INSERT AS SET NOCOUNT ON declare @someid int declare @someid2 int declare @startfrom int declare @test1 varchar(10) select @someid=@@IDENTITY select @test1 = (Select name1 from test2 where sysid = @someid ) if @test1 = 'select' begin insert into Tsel Default values select @someid2 = @@IDENTITY end if @test1 = 'adv' begin insert into Tadv Default values select @someid2 = @@IDENTITY end update test2 set name2=(@someid2) where sysid = @someid SET NOCOUNT OFF

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  • mysql circular dependency in foreign key constraints

    - by Flavius
    Given the schema: What I need is having every user_identities.belongs_to reference an users.id. At the same time, every users has a primary_identity as shown in the picture. However when I try to add this reference with ON DELETE NO ACTION ON UPDATE NO ACTION, MySQL says #1452 - Cannot add or update a child row: a foreign key constraint fails (yap.#sql-a3b_1bf, CONSTRAINT #sql-a3b_1bf_ibfk_1 FOREIGN KEY (belongs_to) REFERENCES users (id) ON DELETE NO ACTION ON UPDATE NO ACTION) I suspect this is due to the circular dependency, but how could I solve it (and maintain referential integrity)?

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  • How do I avoid a race condition in my Rails app?

    - by Cathal
    Hi, I have a really simple Rails application that allows users to register their attendance on a set of courses. The ActiveRecord models are as follows: class Course < ActiveRecord::Base has_many :scheduled_runs ... end class ScheduledRun < ActiveRecord::Base belongs_to :course has_many :attendances has_many :attendees, :through => :attendances ... end class Attendance < ActiveRecord::Base belongs_to :user belongs_to :scheduled_run, :counter_cache => true ... end class User < ActiveRecord::Base has_many :attendances has_many :registered_courses, :through => :attendances, :source => :scheduled_run end A ScheduledRun instance has a finite number of places available, and once the limit is reached, no more attendances can be accepted. def full? attendances_count == capacity end attendances_count is a counter cache column holding the number of attendance associations created for a particular ScheduledRun record. My problem is that I don't fully know the correct way to ensure that a race condition doesn't occur when 1 or more people attempt to register for the last available place on a course at the same time. My Attendance controller looks like this: class AttendancesController < ApplicationController before_filter :load_scheduled_run before_filter :load_user, :only => :create def new @user = User.new end def create unless @user.valid? render :action => 'new' end @attendance = @user.attendances.build(:scheduled_run_id => params[:scheduled_run_id]) if @attendance.save flash[:notice] = "Successfully created attendance." redirect_to root_url else render :action => 'new' end end protected def load_scheduled_run @run = ScheduledRun.find(params[:scheduled_run_id]) end def load_user @user = User.create_new_or_load_existing(params[:user]) end end As you can see, it doesn't take into account where the ScheduledRun instance has already reached capacity. Any help on this would be greatly appreciated.

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  • Phantom activity on MySQL

    - by LoveMeSomeCode
    This is probably just my total lack of MySQL expertise, but is it typical to see lots of phantom activity on a MySQL instance via phpMyAdmin? I have a shared hosting plan through Lithium, and when I log in through the phpMyAdmin console and click on the 'Status' tab, it's showing crazy high numbers for queries. Within an hour of activating my account I had 1 million queries. At first I thought this was them setting things up, but the number is climbing constantly, averaging 170/second. I've got a support ticket in with Lithium, but I thought I'd ask here if this were a MySQL/shared host thing, because I had the same thing happen with a shared hosting plan through Joyent.

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  • I need a mechanism for locating SQL server instances

    - by SzamDev
    Hi I have an idea and I want to apply it to my Application (C# .NET). When we connect to a DB (MS SQL Server 2008) in VS 2008, the ConnectionString saved in the Application Setting and it's a static varriable (no one can edit it unless you edit it inside VS 2008). I want a way to let my Application search for MS SQL Server and save it to Application Setting and use it to connect to my DB Programmatically. When my application start, the first thing to do is checking the ConnectionString if vaild, NOT Empty and test connection to MS SQL Server Successfully so if there is a proplem I think to show a window form to let the user enter some data like username and password for MS SQL Server 2008 Is there any way to do it?

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  • Validation - Data Integrity

    - by Thomas
    A table can only store 10 records in a particular state, 10 users over 30 years for example, the others must be less than 30 years. It is a business rule and as such should be respected. How to ensure that state? Think: multiple users accessing this table.

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  • Could I use urlize filter in this way ?

    - by xRobot
    Could I use urlize filter in this way? : from django.utils.html import urlize def save(self, force_insert=False, force_update=False): self.body = urlize(self.body) super(Post, self).save(force_insert, force_update) body is a TextField.

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  • Create new table with Wordpress API

    - by Fire G
    I'm trying to create a new plugin to track popular posts based on views and I have everything done and ready to go, but I can't seem to create a new table using the Wordpress API (I can do it with standard PHP or with phpMyAdmin, but I want this plugin to be self-sufficient). I've tried several ways ($wpdb-query, $wpdb-get_results, dbDelta) but none of them will create the new table. function create_table(){ global $wpdb; $tablename = $wpdb->prefix.'popular_by_views'; $ppbv_table = $wpdb->get_results("SHOW TABLES LIKE '".$tablename."'" , ARRAY_N); if(is_null($ppbv_table)){ $create_table_sql = "CREATE TABLE '".$tablename."' ( 'id' BIGINT(50) NOT NULL AUTO_INCREMENT, 'url' VARCHAR(255) NOT NULL, 'views' BIGINT(50) NOT NULL, PRIMARY KEY ('id'), UNIQUE ('id') );"; $wpdb->show_errors(); $wpdb->flush(); if(is_null($wpdb->get_results("SHOW TABLES LIKE '".$tablename."'" , ARRAY_N))) echo 'crap, the SQL failed.'; } else echo 'table already exists, nothing left to do.';}

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  • Fluent nHibernate - How to map a non-key column on a junction table?

    - by The Matt
    Taking an example that is provided on the Fluent nHibernate website, I need to extend it slightly: I need to add a 'Quantity' column to the StoreProduct table. How would I map this using nHibernate? An example mapping is provided for the given scenario above, but I'm not sure how I would get the Quantity column to map to a property on the Product class: public class StoreMap : ClassMap<Store> { public StoreMap() { Id(x => x.Id); Map(x => x.Name); HasMany(x => x.Employee) .Inverse() .Cascade.All(); HasManyToMany(x => x.Products) .Cascade.All() .Table("StoreProduct"); } }

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  • Databases: Migrate data between MS Access DB and MYSQL

    - by Dean
    Hello, I have 2 databases, one is MS Access DB from an old website, and the other one is MYSQL from the new Joomla+VirtueMart based website. I need to migrate existing products from MS Access to MYSQL. I thought of putting both on server and writing SQL queries in MYSQL workbench, untill I have a good script for that, but I'm very new to SQL, so I'd rather avoid that. I there a better way and more efficient for that?

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  • Get information from various sources

    - by Francesc
    Hi. I'm developing an app that has to get some information from various sources (APIs and RSS) and display it to the user in near real-time. What's the best way to get it: 1.Have a cron job to update them all accounts every 12h, and when a user is requesting one, update that account, save it to the DB and show it to the user? 2.Have a cron job to update them all accounts every 6h, and when a user is requesting one, update the account and showing it to the user without saving it to the DB? What's the best way to get it? What's faster? And what's the most scallable?

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  • sqlserver how to set job priority

    - by Buzz
    Is there any way to set one job priority higher then other, In my case there are two jobs those are working on same set of tables,first JOB-A which is running every 12 hr and other JOB-B is every 10 minutes , i think at some time when they run simultaneously JOB-B is getting in to deadlock and get failed, i google the topic and found sqlgoverner is helpful in such cases does anyone know how to resolve?

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  • Using a variable derived from a drop-down list as the column name in a select statement ... Access DB

    - by user1459698
    I'm working with the world's worst DB that was already here so don't blame me for that. So, here's what I have so far ... module = txtModule.value presstype = txtPressType.value SQL_query = "SELECT * FROM tbl_spareparts WHERE '"& module &"' <> '""' AND '"& module &"' = '"& presstype &"' AND Manufacturer = '"& txtsrch.value &"' ORDER BY SAP_Part_No" Set rsData = conn.Execute(SQL_query) This brings up the following SQL statement: SELECT * FROM tbl_spareparts WHERE 'Banyan_Module' <> '"' AND 'Banyan_Module' = 'PB' AND Manufacturer = 'Tester' ORDER BY SAP_Part_No Is there any way I can use the module variable as a column name - obviously the ''s around the column name are causing an error. This is really bothering me. BTW, I'm writing this in VBScript inside a .HTA application page as it has to run locally on tech PCs. Thanks. R.

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  • MySQL "NULL" questions

    - by Camran
    I have a table with several columns. Sometimes some of these column fields may be empty (ie. I won't use them in some cases). My questions: Would it be smart to set them to NULL in phpmyadmin? What does the "NULL" property actually do? Would I gain anything at all by setting them to NULL? Is it possible to use a NULL field the same way even though it is set to null?

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  • Alter multiple tables' columns length

    - by gdoron
    So, we just found out that 254 tables in our Oracle DBMS have one column named "Foo" with the wrong length- Number(10) instead of Number(3). That foo column is a part from the PK of the tables. Those tables have other tables with forigen keys to it. What I did is: backed-up the table with a temp table. Disabled the forigen keys to the table. Disabled the PK with the foo column. Nulled the foo column for all the rows. Restored all the above But now we found out it's not just couple of tables but 254 tables. Is there an easy way, (or at least easier than this) to alter the columns length? P.S. I have DBA permissions.

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  • Should I sanitize EVERY form variable passed along?

    - by Camran
    I have a form with many fields... The action is set to a php page which queries mysql... Should I sanitize with mysql_real_escape_string every single variable? Or can I ignore sanitizing drop-lists and radios for instance? Also, besides mysql_real_escape_string, what else should I do to prevent attacks? Thanks

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  • If I take a large datatype. Will it affect performance in sql server

    - by Shantanu Gupta
    If i takes larger datatype where i know i should have taken datatype that was sufficient for possible values that i will insert into a table will affect any performance in sql server in terms of speed or any other way. eg. IsActive (0,1,2,3) not more than 3 in any case. I know i must take tinyint but due to some reasons consider it as compulsion, i am taking every numeric field as bigint and every character field as nVarchar(Max) Please give statistics if possible, to let me try to overcoming that compulsion. I need some solid analysis that can really make someone rethink before taking any datatype.

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  • How to configure DB connection in a Servlet based JPA application

    - by deamon
    By default DB connections of JPA applications are configured in the META-INF/persistence.xml, when the application is not deployed to a full Java EE application server. In my opinion it is not very elegant to place such environment specific configuration into a file that is inside a .war file. How could a DB connection of a Servlet based JPA application be configured more flexible (=outside of the .war file)?

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  • How should I migrate DDL changes from one environment to the next?

    - by Rl
    I make DDL changes using SQL Developer's GUI. Problem is, I need to apply those same changes to the test environment. I'm wondering how others handle this issue. Currently I'm having to manually write ALTER statements to bring the test environment into alignment with the development environment, but this is prone to error (doing the same thing twice). In cases where there's no important data in the test environment I usually just blow everything away, export the DDL scripts from dev and run them from scratch in test. I know there are triggers that can store each DDL change, but this is a heavily shared environment and I would like to avoid that if possible. Maybe I should just write the DDL stuff manually rather than using the GUI?

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  • How to Deal with SET ANSI_NULLS ON or OFF ?

    - by Shantanu Gupta
    I want to call this procedure that sends one value that can be NULL or any int value. SELECT DomainName, DomainCode FROM Tags.tblDomain WHERE SubDomainId =@SubDomainId I simply want to use this single query rather than what i m doing right now in below given code. I searched for this how could i do this then i got this Link. According to this I have to set ANSI_NULLS OFF I am not able to set this inside this procedure before executing my sql query and then reset it again after doing this. ALTER PROCEDURE [Tags].[spOnlineTest_SubDomainSelect] @SubDomainId INT AS BEGIN -- SET NOCOUNT ON added to prevent extra result sets from -- interfering with SELECT statements. SET NOCOUNT ON; -- Insert statements for procedure here IF @SubDomainId IS NULL SELECT DomainName, DomainCode FROM Tags.tblDomain WHERE SubDomainId IS NULL ELSE SELECT DomainName, DomainCode FROM Tags.tblDomain WHERE SubDomainId =@SubDomainId END What will be the better practice to do deal with ANSI_NULLS or Using If Else

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