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• Postgres user/role drop

  - by Grasper

  I am trying to drop a user: drop user testUser; I want to force this to work in a simple manner (Not a million calls)... How can I do this easily? I get this output: ERROR: role "testUser" cannot be dropped because some objects depend on it DETAIL: access to table main.tap_db_version access to table main.user_instance access to table main.target_type access to table main.status_code access to table main.state_space_profile access to table main.service_subscription access to table main.service_instance access to table main.sa_ordnance_weapon_type access to table main.operation access to table main.mission_class access to table main.map_symbol access to table main.ada_weapon_type access to table main.active_process access to table main.acft_type_00_only access to table main.abp_create_params access to table main.exercise access to table main.decl access to table main.data_set access to table main.cancellation_notice access to table main.ato_family_tree access to table main.apportionment_cat_cd access to table main.abp access to table main.alert_settings access to table main.alert_log access to table main.airspace_usage_category access to schema main access to view testUser.top_priority access to view testUser.target_ssm_msn_count access to view testUser.target_air_msn_count access to view testUser.sortie_sum access to view testUser.ref_info access to view testUser.preview_rmk_count access to view testUser.preview_pgm_las_count access to view testUser.preview_pgm_desi_count access to view testUser.preview_objective_count access to view testUser.preview_gfriend_count access to view testUser.preview_escort_msn_req access to view testUser.preview_chaff_data access to view testUser.preview_airmove_seg access to view testUser.preview_aircraft_total access to view testUser.offload_total access to view testUser.objective_count access to view testUser.fuel_planned access to view testUser.ew_data access to view testUser.dual access to view testUser.current_base_inventory access to view testUser.cell_total access to view testUser.asgn_sortie_sum access to view testUser.appor_sorties_planned access to view testUser.airmove_seg access to view testUser.aircraft_total access to view testUser.abp access to table testUser.req_msn_task access to table testUser.req_task_source_req access to table testUser.req_ssm_msn access to table testUser.req_ssm_source access to table testUser.req_msn access to table testUser.req_msn_warnings access to table testUser.req_air_msn access to table testUser.req_src_header access to table testUser.req_msn_ids access to table testUser.req_msn_comment access to table testUser.req_c2_msn access to table testUser.req_c2_source access to table testUser.req_ada_msn access to table testUser.req_ada_vertex access to table testUser.weather_forecast access to table testUser.weather_coords access to table testUser.weather_area access to table testUser.weapon_option access to table testUser.wag_activity access to table testUser.unit_remark access to table testUser.unit_location_turn access to table testUser.unit_iff access to table testUser.unit_coordination access to table testUser.unit_code access to table testUser.trace_point access to table testUser.tasking_agency access to table testUser.task_unit access to table testUser.target_type access to table testUser.tap_db_version access to table testUser.status_code access to table testUser.state_space_threat access to table testUser.state_space_profile access to table testUser.state_space access to table testUser.ssm_mission access to table testUser.spins_section_id access to table testUser.spins_codes access to table testUser.spins access to table testUser.unit_location access to table testUser.ship_target_request access to table testUser.service_subscription access to table testUser.service_instance access to table testUser.sa_ordnance_weapon_type access to table testUser.runway access to table testUser.restricted_codes access to table testUser.response_entity access to table testUser.residual_mission access to table testUser.request_objective access to table testUser.request and 194 other objects (see server log for list)

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• Abstract Factory design pattern to create objects? Why can’t we just use the new operator?

  - by Harsha

  why do we need a Abstract Factory design pattern to create objects? Why can’t we just use the new operator? answer is, to avoid tight coupleing of the objects. But I didn't understand how ? can anyone explain with code (will be very useful). what makes abstract factory design pattern useful and when. Thanks in advance. Harsha T

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• In a One to One relationship should i drop one of the table's id column?

  - by Vlad

  I have the following 2 tables in MySQL: Customer(Id, Firstname, Lastname...) Bonus(Id, CustomerId, Value, ...) The relation is One-To-One, every customer has only one bonus.(the CustomerId is unique in the Bonus Table) Q: Should I drop the Id column of the Bonus table? (I want to know why or why not)

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• How to implement an offline reader writer lock

  - by Peter Morris

  Some context for the question All objects in this question are persistent. All requests will be from a Silverlight client talking to an app server via a binary protocol (Hessian) and not WCF. Each user will have a session key (not an ASP.NET session) which will be a string, integer, or GUID (undecided so far). Some objects might take a long time to edit (30 or more minutes) so we have decided to use pessimistic offline locking. Pessimistic because having to reconcile conflicts would be far too annoying for users, offline because the client is not permanently connected to the server. Rather than storing session/object locking information in the object itself I have decided that any aggregate root that may have its instances locked should implement an interface ILockable public interface ILockable { Guid LockID { get; } } This LockID will be the identity of a "Lock" object which holds the information of which session is locking it. Now, if this were simple pessimistic locking I'd be able to achieve this very simply (using an incrementing version number on Lock to identify update conflicts), but what I actually need is ReaderWriter pessimistic offline locking. The reason is that some parts of the application will perform actions that read these complex structures. These include things like Reading a single structure to clone it. Reading multiple structures in order to create a binary file to "publish" the data to an external source. Read locks will be held for a very short period of time, typically less than a second, although in some circumstances they could be held for about 5 seconds at a guess. Write locks will mostly be held for a long time as they are mostly held by humans. There is a high probability of two users trying to edit the same aggregate at the same time, and a high probability of many users needing to temporarily read-lock at the same time too. I'm looking for suggestions as to how I might implement this. One additional point to make is that if I want to place a write lock and there are some read locks, I would like to "queue" the write lock so that no new read locks are placed. If the read locks are removed withing X seconds then the write lock is obtained, if not then the write lock backs off; no new read-locks would be placed while a write lock is queued. So far I have this idea The Lock object will have a version number (int) so I can detect multi-update conflicts, reload, try again. It will have a string[] for read locks A string to hold the session ID that has a write lock A string to hold the queued write lock Possibly a recursion counter to allow the same session to lock multiple times (for both read and write locks), but not sure about this yet. Rules: Can't place a read lock if there is a write lock or queued write lock. Can't place a write lock if there is a write lock or queued write lock. If there are no locks at all then a write lock may be placed. If there are read locks then a write lock will be queued instead of a full write lock placed. (If after X time the read locks are not gone the lock backs off, otherwise it is upgraded). Can't queue a write lock for a session that has a read lock. Can anyone see any problems? Suggest alternatives? Anything? I'd appreciate feedback before deciding on what approach to take.

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• recursive delete trigger and ON DELETE CASCADE contraints are not deleting everything

  - by bitbonk

  I have a very simple datamodel that represents a tree structure: The RootEntity is the root of such a tree, it can contain children of type ContainerEntity and of type AtomEntity. The type ContainerEntity again can contain children of type ContainerEntity and of type AtomEntity but can not contain children of type RootEntity. Children are referenced in a well known order. The DB model for this is below. My problem now is that when I delete a RootEntity I want all children to be deleted recursively. I have create foreign key with CASCADE DELETE and two delete triggers for this. But it is not deleting everything, it always leaves some items in the ContainerEntity, AtomEntity, ContainerEntity_Children and AtomEntity_Children tables. Seemling beginning with the recursionlevel of 3. CREATE TABLE RootEntity ( Id UNIQUEIDENTIFIER NOT NULL, Name VARCHAR(500) NOT NULL, CONSTRAINT PK_RootEntity PRIMARY KEY NONCLUSTERED (Id), ); CREATE TABLE ContainerEntity ( Id UNIQUEIDENTIFIER NOT NULL, Name VARCHAR(500) NOT NULL, CONSTRAINT PK_ContainerEntity PRIMARY KEY NONCLUSTERED (Id), ); CREATE TABLE AtomEntity ( Id UNIQUEIDENTIFIER NOT NULL, Name VARCHAR(500) NOT NULL, CONSTRAINT PK_AtomEntity PRIMARY KEY NONCLUSTERED (Id), ); CREATE TABLE RootEntity_Children ( ParentId UNIQUEIDENTIFIER NOT NULL, OrderIndex INT NOT NULL, ChildContainerEntityId UNIQUEIDENTIFIER NULL, ChildAtomEntityId UNIQUEIDENTIFIER NULL, ChildIsContainerEntity BIT NOT NULL, CONSTRAINT PK_RootEntity_Children PRIMARY KEY NONCLUSTERED (ParentId, OrderIndex), -- foreign key to parent RootEntity CONSTRAINT FK_RootEntiry_Children__RootEntity FOREIGN KEY (ParentId) REFERENCES RootEntity (Id) ON DELETE CASCADE, -- foreign key to referenced (child) ContainerEntity CONSTRAINT FK_RootEntiry_Children__ContainerEntity FOREIGN KEY (ChildContainerEntityId) REFERENCES ContainerEntity (Id) ON DELETE CASCADE, -- foreign key to referenced (child) AtomEntity CONSTRAINT FK_RootEntiry_Children__AtomEntity FOREIGN KEY (ChildAtomEntityId) REFERENCES AtomEntity (Id) ON DELETE CASCADE, ); CREATE TABLE ContainerEntity_Children ( ParentId UNIQUEIDENTIFIER NOT NULL, OrderIndex INT NOT NULL, ChildContainerEntityId UNIQUEIDENTIFIER NULL, ChildAtomEntityId UNIQUEIDENTIFIER NULL, ChildIsContainerEntity BIT NOT NULL, CONSTRAINT PK_ContainerEntity_Children PRIMARY KEY NONCLUSTERED (ParentId, OrderIndex), -- foreign key to parent ContainerEntity CONSTRAINT FK_ContainerEntity_Children__RootEntity FOREIGN KEY (ParentId) REFERENCES ContainerEntity (Id) ON DELETE CASCADE, -- foreign key to referenced (child) ContainerEntity CONSTRAINT FK_ContainerEntity_Children__ContainerEntity FOREIGN KEY (ChildContainerEntityId) REFERENCES ContainerEntity (Id) ON DELETE CASCADE, -- foreign key to referenced (child) AtomEntity CONSTRAINT FK_ContainerEntity_Children__AtomEntity FOREIGN KEY (ChildAtomEntityId) REFERENCES AtomEntity (Id) ON DELETE CASCADE, ); CREATE TRIGGER Delete_RootEntity_Children ON RootEntity_Children FOR DELETE AS DELETE FROM ContainerEntity WHERE Id IN (SELECT ChildContainerEntityId FROM deleted) DELETE FROM AtomEntity WHERE Id IN (SELECT ChildAtomEntityId FROM deleted) GO CREATE TRIGGER Delete_ContainerEntiy_Children ON ContainerEntity_Children FOR DELETE AS DELETE FROM ContainerEntity WHERE Id IN (SELECT ChildContainerEntityId FROM deleted) DELETE FROM AtomEntity WHERE Id IN (SELECT ChildAtomEntityId FROM deleted) GO

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• Synonym for "Many-to-Many" relationship (relational databases)

  - by Byron

  What's a synonym for a "many-to-many" relationship? I've finished writing an object-relational mapper but I'm still stumped as to what to name the function that adds that relation. addParent() and addChild() seemed quite logical for the many-to-one/one-to-many and addSuperclass() for one-to-one inheritance, but addManyToMany() would sound quite unintuitive to an object-oriented programmer. addSibling() or addCousin() doesn't really make sense either. Any suggestions? And before you dismiss this as a non-programming question, please remember that consistent naming schemes and encapsulation are pretty integral to programming :)

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• Should this even be a has_many :through association?

  - by GoodGets

  A Post belongs_to a User, and a User has_many Posts. A Post also belongs_to a Topic, and a Topic has_many Posts. class User < ActiveRecord::Base has_many :posts end class Topic < ActiveRecord::Base has_many :posts end class Post < ActiveRecord::Base belongs_to :user belongs_to :topic end Well, that's pretty simple and very easy to set up, but when I display a Topic, I not only want all of the Posts for that Topic, but also the user_name and the user_photo of the User that made that Post. However, those attributes are stored in the User model and not tied to the Topic. So how would I go about setting that up? Maybe it can already be called since the Post model has two foreign keys, one for the User and one for the Topic? Or, maybe this is some sort of "one-way" has_many through assiociation. Like the Post would be the join model, and a Topic would has_many :users, :through = :posts. But the reverse of this is not true. Like a User does NOT has_many :topics. So would this even need to be has_many :though association? I guess I'm just a little confused on what the controller would look like to call both the Post and the User of that Post for a give Topic. Edit: Seriously, thank you to all that weighed in. I chose tal's answer because I used his code for my controller; however, I could have just as easily chosen either j.'s or tim's instead. Thank you both as well. This was so damn simple to implement, and I think today marks the day that I'm beginning to fall in love with rails.

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• GORM ID generation and belongsTo association ?

  - by fabien-barbier

  I have two domains : class CodeSetDetail { String id String codeSummaryId static hasMany = [codes:CodeSummary] static constraints = { id(unique:true,blank:false) } static mapping = { version false id column:'code_set_detail_id', generator: 'assigned' } } and : class CodeSummary { String id String codeClass String name String accession static belongsTo = [codeSetDetail:CodeSetDetail] static constraints = { id(unique:true,blank:false) } static mapping = { version false id column:'code_summary_id', generator: 'assigned' } } I get two tables with columns: code_set_detail: code_set_detail_id code_summary_id and code_summary: code_summary_id code_set_detail_id (should not exist) code_class name accession I would like to link code_set_detail table and code_summary table by 'code_summary_id' (and not by 'code_set_detail_id'). Note : 'code_summary_id' is define as column in code_set_detail table, and define as primary key in code_summary table. To sum-up, I would like define 'code_summary_id' as primary key in code_summary table, and map 'code_summary_id' in code_set_detail table. How to define a primary key in a table, and also map this key to another table ?

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• Best way to fetch data from a single database table with multiple threads?

  - by Ravi Bhatt

  Hi, we have a system where we collect data every second on user activity on multiple web sites. we dump that data into a database X (say MS SQL Server). we now need to fetch data from this single table from daatbase X and insert into database Y (say mySql). we want to fetch time based data from database X through multiple threads so that we fetch as fast as we can. Once fetched and stored in database Y, we will delete data from database X. Are there any best practices on this sort of design? any specific things to take care on table design like sharing or something? Are there any other things that we need to take care to make sure we fetch it as fast as we can from threads running on multiple machines? Thanks in advance! Ravi

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• Program to find canonical cover or minimum number of functional dependencies

  - by Sev

  I would like to know if there is a program or algorithm to find canonical cover or minimum number of functional dependencies? For example: If you have: R = (A,B,C) <-- these are tables: A,B,C And dependencies: A ? BC B ? C A ? B AB ? C The canonical cover (or minimum number of dependencies) is: A ? B B ? C Is there a program that can accomplish this? If not, any code/pseudocode to help me write one would be appreciated. Prefer in Python or Java.

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• add schema to path in postgresql

  - by veilig

  I'm the process of moving applications over from all in the public schema to each having their own schema. for each application, I have a small script that will create the schema and then create the tables,functions,etc... to that schema. Is there anyway to automatically add a newly created schema to the search_path? Currently, the only way I see is to find the users current path SHOW search_path; and then add the new schema to it SET search_path to xxx,yyy,zzz; I would like some way to just say, append schema zzz to the users_search path. is this possible?

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• Best solution for a comment table for multiple content types

  - by KRTac

  I'm currently designing a comments table for a site I'm building. Users will be able to upload images, link videos and add audio files to the profile. Each of these types of content must be commentable. Now I'm wondering what's the best approach to this. My current options are: 1. to have one big comments table and a link tables for every content type (comments_videos, ...) with comment_id and _id. 2. to have comments separated by the type of content their for. So each type of content would have his own comments table with the comments for that type.

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• I want define tables from ER Diagram.

  - by M R Jafari

  I have a unary relationship. (Image Url : http://freezpic.com/pics/666c94955212a2f757fa25f9f7d31a5e.png) But I want define a table for person. The table has personID and personName column. What columns add it?

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• Examples of "when is good idea implement many-to-many relationships"?

  - by panchicore

  I ask this because need to understand/explain better with examples. clasical examples like: an Article can be published in multiple Publication objects, and a Publication has multiple Article objects. (source) I see is usefull for web2.0 for sharing features.

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• Entity framework (1): implement 1 foreign key to multiple tables

  - by Michel

  Hi, i've modeled this: i have an import table, and an import steps table import 1 .. N importsteps Now i have a table importparams, which hold key/value pairs to register all kind of info about the import or the importsteps. So i have modeled a FK in SqlServer which points to the PK of the import table and to the PK of the importsteps table (the ID's for both the import as the importsteps table are guids, so i can query the importparams with either the id from import or from importsteps and get the right importparams). Makes sense a bit? But how can i model this in the EF? I can see it's a bit hard for the EF to model this, because one realtion can point to multiple classes, but is there a way? The workaround normally is just to get all importparams where FK is the ID, but as you know the FK is not available in the EF version 1. I hope you can help me out, michel

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• Where do you start your design - code, UI or workflow?

  - by Mmarquee

  Hi I was discussing this at work, and was wondering where people start their designs? We tend to start with designing code to solve the problem presented to us, but that is probably all of us are (or were) programmers. I was wondering where other people and organisations start their design. Do they start with solving the problem as a coding problem, sit down and design what UI to use, or map out the data or workflow? Thanks

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• Two different tables or just one with bool column?

  - by Aidas

  We have two tables: OriginalDocument and ProcessedDocument. In the first one we put an original, not processed document. After it's validated and processed (converted to our xml format and parsed), it's put into Document table. Processed document can be valid or invalid. Which makes more sense: have two different tables for valid and invalid documents or just have one with 'Valid' column? Some of the columns (~5-7) are irrelevant for invalid document. Storing both invalid and valid documents would also make Document table filled with 'NULL' columns (if document is invalid, information like document number, receiver can be unknown). What else should we consider and weigh, when making this decision?

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• Data Modeling of Entity with Attributes

  - by StackOverflowNewbie

  I'm storing some very basic information "data sources" coming into my application. These data sources can be in the form of a document (e.g. PDF, etc.), audio (e.g. MP3, etc.) or video (e.g. AVI, etc.). Say, for example, I am only interested in the filename of the data source. Thus, I have the following table: DataSource Id (PK) Filename For each data source, I also need to store some of its attributes. Example for a PDF would be "numbe of pages." Example for audio would be "bit rate." Example for video would be "duration." Each DataSource will have different requirements for the attributes that need to be stored. So, I have modeled "data source attribute" this way: DataSourceAttribute Id (PK) DataSourceId (FK) Name Value Thus, I would have records like these: DataSource->Id = 1 DataSource->Filename = 'mydoc.pdf' DataSource->Id = 2 DataSource->Filename = 'mysong.mp3' DataSource->Id = 3 DataSource->Filename = 'myvideo.avi' DataSourceAttribute->Id = 1 DataSourceAttribute->DataSourceId = 1 DataSourceAttribute->Name = 'TotalPages' DataSourceAttribute->Value = '10' DataSourceAttribute->Id = 2 DataSourceAttribute->DataSourceId = 2 DataSourceAttribute->Name = 'BitRate' DataSourceAttribute->Value '16' DataSourceAttribute->Id = 3 DataSourceAttribute->DataSourceId = 3 DataSourceAttribute->Name = 'Duration' DataSourceAttribute->Value = '1:32' My problem is that this doesn't seem to scale. For example, say I need to query for all the PDF documents along with thier total number of pages: Filename, TotalPages 'mydoc.pdf', '10' 'myotherdoc.pdf', '23' ... The JOINs needed to produce the above result is just too costly. How should I address this problem?

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• Tables as relations in ER diagrams

  - by Richard Mar.

  Assume I have the following tables (**bold** - primary key, *italics* - foreign key): patient(**patient_id**, name) disease(**disease_id**, name) patient_disease(**p_d_id**, *patient_id*, *disease,_id* ) I want to draw the ER diagram for this. My idea is to make two entities, one for patient and one for disease, then make a n-to-n relation between them, with p_d_id as its attribute. Is that how it's supposed to be?

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• What is an index in MySQL?

  - by Eric

  http://i.imgur.com/JdsUK.jpg I created a table like the picture above. What are the "Indexes"? primary key? unique? It works well without setting indexes.. What do they do? why do I need them? Also, I set all String fields to TEXT because I didn't know how many characters I need. Is this a good idea? I don't see any difference. Thanks!

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• django models : How to have variable number of foreign keys in a model ?

  - by Rohit

  For instance, Model Resume contains variable number of Model Project 's, What should be my models and relationships between them to achieve this ? Thanks in advance.

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• How to force grails GORM to respect DB scheme ?

  - by fabien-barbier

  I have two domains : class CodeSet { String id String owner String comments String geneRLF String systemAPF static hasMany = [cartridges:Cartridge] static constraints = { id(unique:true,blank:false) } static mapping = { table 'code_set' version false columns { id column:'code_set_id', generator: 'assigned' owner column:'owner' comments column:'comments' geneRLF column:'gene_rlf' systemAPF column:'system_apf' } } and : class Cartridge { String id String code_set_id Date runDate static belongsTo = CodeSet static constraints = { id(unique:true,blank:false) } static mapping = { table 'cartridge' version false columns { id column:'cartridge_id', generator: 'assigned' code_set_id column:'code_set_id' runDate column:'run_date' } } Actually, with those models, I get tables : - code_set, - cartridge, - and table : code_set_cartridge (two fields : code_set_cartridges_id, cartridge_id) I would like to not have code_set_cartridge table, but keep relationship : code_set -- 1:n -- cartridge In other words, how can I keep association between code_set and cartridge without intermediate table ? (using code_set_id as primary key in code_set and code_set_id as foreign key in cartridge). Mapping with GORM can be done without intermediate table?

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• Common one-to-many table for multiple entities

  - by Ben V

  Suppose I have two tables, Customer and Vendor. I want to have a common address table for customer and vendor addresses. Customers and Vendors can both have one to many addresses. Option 1 Add columns for the AddressID to the Customer and Vendor tables. This just doesn't seem like a clean solution to me. Customer Vendor Address -------- --------- --------- CustomerID VendorID AddressID AddressID1 AddressID1 Street AddressID2 AddressID2 City... Option 2 Move the foreign key to the Address table. For a Customer, Address.CustomerID will be populated. For a Vendor, Address.VendorID will be populated. I don't like this either - I shouldn't need to modify the address table every time I want to use it for another entity. Customer Vendor Address -------- --------- --------- CustomerID VendorID AddressID CustomerID VendorID Option 3 I've also seen this - only 1 foreign key column on the Address table with another column to identify which foreign key table the address belongs to. I don't like this one because it requires all the foreign key tables to have the same type of ID. It also seems messy once you start coding against it. Customer Vendor Address -------- --------- --------- CustomerID VendorID AddressID FKTable FKID So, am I just too picky, or is there something I haven't thought of?

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• Oracle - Is there any effects of not having a primary key on a table ?

  - by Sathya

  We use sequence numbers for primary keys on the tables. There are some tables where we dont really use the primary key for any querying purpose. But, we have Indexes on other columns. These are non-unique indexes. The queries use these non-primary key columns in the WHERE conditions. So, I dont really see any benefit of having a primary key on such tables. My experience with SQL 2000 was that, it used to replicate tables which had some primary key. Otherwise it would not. I am using Oracle 10gR2. I would like to know if there are any such side-effects of having tables that dont have primary key.

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• Where do you start your design - code, UI, workflow or whatever?

  - by Mmarquee

  Hi I was discussing this at work, and was wondering where people start their designs? We tend to start with designing code to solve the problem presented to us, but that is probably all of us are (or were) programmers. I was wondering where other people and organisations start their design. Do they start with solving the problem as a coding problem, sit down and design what UI to use, or map out the data or workflow? Thanks

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