primary-key

SQL Server how to maintain GUID across tables in same DB

I want to create a DB , where each table's PK will be GUID and which will be unique across the DB, Example: my DB name is 'LOCATION'. And I have 3 table as 'CITY' , 'STATE' and 'COUNTRY'. I want that all the 3 tables have same PK field as GUID ,and that value will be unique across DB. How to do this in SQL Server, any idea? I have n...

newid() vs newsequentialid() What are the differences/pros and cons?

In a database where all of your primary keys are GUIDs, what are the differences/implications and/or pros and cons using newid() versus newsequentialid() as the "default value or binding". The only difference that I know of is that newid() creates a new random GUID as opposed to newsequentialid() creates a new GUID based on the last one...

SQL Server: drop table primary key, without knowing its name

HI, Using: SQL Server Database: Northwind I'd like to drop a table primary key, without knowing the PK constraint name.. eg, using the Categories table in the Northwind Sample database, the primary key column is 'CategoryId', and the primary key name is 'PK_Categories' I can drop the primary key while knowing the primary key name: A...

Mysql: How do you create a table with multiple primary keys?

I have this situation: http://stackoverflow.com/questions/1590033/mysql-newbie-question-which-are-the-pk-and-the-fk-for-this-tables (take a look at the table Salaries) How do you create a table with multiple primary keys? create table salaries ( dep_id smallint auto_increment primary key, emp_id smallint auto_increment primary ke...

Increase increment size to match GUID advantage

Hi, I've been thinking of implementing this system, but can't help but feel there's a catch somewhere. One of the points of using GUID over incrementing int is that, in the future, if you were to merge databases together, you wouldn't have any clashes over the primary key/identifier. However, my approach is to set the increment size t...

Constraint Exception when copying table?

I'm experiencing some weird behavior when trying to modify some DataTable objects. Upon the second call to the subroutine, I get the following error when I to copy the source DataTable to a working set: System.Data.ConstraintException was caught Message="Column 'pk' is constrained to be unique. Value 'path0.tag0' is already...

Mysql auto increment primary key id's

I have some mysql tables that have auto incrementing id's that are primary keys, but I notice that I never actually use them... I used to think that every table must have a primary key so I guess that is why I created them before. Should I remove them all if I don't use them at all? ...

About primary key in the table?

I would like to have some explaination about the characteristics of a primary key in the table of such database.This is for vb 2008 express edition,since im new to this language,if this is true, as far as i understand about the characteristic in setting the primary key on each field for true.My question is if you are doing an updates/edi...

trap of primary key error

hi expert, i wants to trap sql-2000 primary key error into c# and develop my own error like "this is duplicate Invoice Number" kindly reply how to do this in c# application. Thanx. ...

Storing SHA1 Signature as Primary Key in Postgres SQL

Hi, I'm writing a simple content management system. I need to store SHA1 hash values that are computed externally as the primary key for my biggest table. I can obviously use a sequence as a primary key and index the SHA1 hex-string for look-up... However, I'm looking for a more elegant solution, where I will simply use the 20-byte SHA1...

Is it a good idea to use rowguid as unique key in database design?

Hi there, SQL Server provides the type [rowguid]. I like to use this as unique primary key, to identify a row for update. The benefit shows up if you dump the table and reload it, no mess with SerialNo (identity) columns. In the special case of distributed databases like offline copies on notebooks or something like that, nothing else ...

Should i have a primary ID? i am indexing another field.

Using sqlite i need a table to hold a blob to store a md5 hash and a 4byte int. I plan to index the int but this value will not be unique. Do i need a primary key for this table? and is there an issue with indexing a non unique value? (I assume there is not issue or reason for any). ...

Should I add a autoinc primary key for the sake of having a primary key?

I have a table which needs 2 fields. One will be a foreign key, the other is not necessarily unique. There really isn't a reason that I can find to have a primary key other than having read that "every single tabel ever needs needs needs a primary key". Edit: Some good thoughts in here. For clarity's sake, I will give you an example t...

mysql - Able to enter multiple values even when new value equals an existing primary key

I have a table defined as follows: CREATE TABLE `mydb`.`users` ( `userID` int(10) unsigned NOT NULL AUTO_INCREMENT, `userName` varchar(100) COLLATE utf8_unicode_ci NOT NULL, `createdDate` datetime NOT NULL, `active` tinyint(1) NOT NULL, `lastUpdatedDate` datetime NOT NULL, PRIMARY KEY (`userID`,`userName`) USING BTREE ) H...

Fabricate entities with multiple IDENTITY PKs?

Disclosure: I'm a 'natural key' advocate myself and averse to the IDENTITY PK approach. But I do have a 'live and let live' approach to lifestyle choices, so no religious arguments here please :) I have inherited a table where the only key is the IDENTITY PK column; let's call it ID. There are a many tables that reference ID. The intend...

Rails modeling: converting HABTM to has_many :through

I'm doing maintenance work on an existing Rails site and am having some problems stemming from many-to-many associations. It looks like the site was initially built using has_and_belongs_to_many for a few relationships that have since gotten more complicated in the business logic, so I need to use has_many :through instead to support ad...

Primary Key behaviour in Core Data iPhone

I am making an app that parses feeds from xml and stores them using Core Data. The issue I am dealing with at the moment is duplicate entries. Every feed I am parsing contains a unique id, something that I get in my model as an int. Now what I need is to tell Core Data not to store that entity if another with the same id already exists. ...

When not to use surrogate primary keys?

I have several database tables that just contain a single column and very few rows, often just an ID of something defined in another system. These tables are then referenced with foreign keys from other tables. For example one table contains country codes (SE, DK, US etc). All values are always unique natural keys and they are used as p...

is it good to have primary keys as Identity field

Hi , I have read a lot of articles about whether we should have primary keys that are identity columns, but I'm still confused. There are advantages of making columns are identity as it would give better performance in joins and provides data consistency. But there is a major drawback associated with identity ,i.e.When INSERT statement ...

DataSet and Primary Key with multiple columns

How Can I use Find method in DataSet that has Primary Key make of 3 Columns? dadSample.SelectCommand = New SqlCommand("SELECT * FROM StockBalance", conxMain) dadSample.FillSchema(dsSample, SchemaType.Source, "StockBalance") dadSample.Fill(dsSample, "Stock") Dim keyColStock(3) As DataColumn keyCol...