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• Discover intended Foreign Keys from JOINS in scripts

  - by Jason

  I'm inheriting a database that has 400 tables and only 150 foreign key constraints registered. Knowing what I do about the application and looking at the table columns, it's easy to say that there ought to be a lot more. I'm afraid that the current application software will break if I started adding the missing FKs because the developers have probably come to rely on this "freedom", but step one in fixing the problem is to come up with the list of missing FKs so we can evaluate them as a team. To make matters worse, the referencing columns don't share a naming convention. The relationships ARE coded informally into the hundreds of ad-hoc queries and stored procedures, so my hope is to parse these files programmatically looking for JOINS between actual tables (but not table variables, etc). Challenges I foresee in this approach are: newlines, optional aliases and table hints, alias resolution. Any better ideas? (Besides quitting) Are there any pre-built tools that can solve this? I don't think regex can handle this. Do you disagree? SQL Parsers? I tried using Microsoft.SqlServer.Management.SqlParser.Parser but all that is exposed is the lexer - can't get an AST out of it - all that stuff is internal.

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• JPA : many-to-many - only one foreign key in the association table

  - by Julien

  Hi, I mapped two classes in a ManyToMany association with these annotations : @Entity @Inheritance(strategy=InheritanceType.TABLE_PER_CLASS) public abstract class TechnicalItem extends GenericBusinessObject implements Resumable{ @SequenceGenerator(name="TECHNICAL_ITEM_ID_GEN", sequenceName="TECHNICAL_ITEM_ID_SEQ") @Id @Column(name = "\"ID\"", nullable = false) @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "TECHNICAL_ITEM_ID_GEN") private int id; @ManyToMany(mappedBy = "referencePerformanceItems", fetch=FetchType.LAZY) private List testingRates; } @Entity @DiscriminatorValue("T") public class TestingRate extends Rate { @ManyToMany(fetch=FetchType.LAZY) @JoinTable(name="ecc.\"TESTING_RATE_TECHNICAL_ITEM\"", joinColumns = {@JoinColumn(name = "\"TESTING_RATE_ID\"")}, inverseJoinColumns = {@JoinColumn(name = "\"TECHNICAL_ITEM_ID\"")}) //@ManyToMany(mappedBy = "testingRates", fetch=FetchType.LAZY) private List referencePerformanceItems; } The sql generated for the association table creation is : create table ecc."TESTING_RATE_TECHNICAL_ITEM" ( "TESTING_RATE_ID" int4 not null, "TECHNICAL_ITEM_ID" int4 not null ); alter table ecc."TESTING_RATE_TECHNICAL_ITEM" add constraint FKC5D64DF6A2FE2698 foreign key ("TESTING_RATE_ID") references ecc."RATE"; There is no mention of the second foreign key "TECHNICAL_ITEM_ID" (the second part of the composite foreign key which should be in the association table). Is it a normal behaviour ? What should I do in the mapping if I want my 2 columns are 2 foreign keys referencing the primary keys of my 2 concerned tables. I use a PostGreSQL database and Hibernate as JPA provider. Thanks, Julien

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• PostgreSQL, Foreign Keys, Insert speed & Django

  - by Miles

  A few days ago, I ran into an unexpected performance problem with a pretty standard Django setup. For an upcoming feature, we have to regenerate a table hourly, containing about 100k rows of data, 9M on the disk, 10M indexes according to pgAdmin. The problem is that inserting them by whatever method literally takes ages, up to 3 minutes of 100% disk busy time. That's not something you want on a production site. It doesn't matter if the inserts were in a transaction, issued via plain insert, multi-row insert, COPY FROM or even INSERT INTO t1 SELECT * FROM t2. After noticing this isn't Django's fault, I followed a trial and error route, and hey, the problem disappeared after dropping all foreign keys! Instead of 3 minutes, the INSERT INTO SELECT FROM took less than a second to execute, which isn't too surprising for a table <= 20M on the disk. What is weird is that PostgreSQL manages to slow down inserts by 180x just by using 3 foreign keys. Oh, disk activity was pure writing, as everything is cached in RAM; only writes go to the disks. It looks like PostgreSQL is working very hard to touch every row in the referred tables, as 3MB/sec * 180s is way more data than the 20MB this new table takes on disk. No WAL for the 180s case, I was testing in psql directly, in Django, add ~50% overhead for WAL logging. Tried @commit_on_success, same slowness, I had even implemented multi row insert and COPY FROM with psycopg2. That's another weird thing, how can 10M worth of inserts generate 10x 16M log segments? Table layout: id serial primary, a bunch of int32, 3 foreign keys to small table, 198 rows, 16k on disk large table, 1.2M rows, 59 data + 89 index MB on disk large table, 2.2M rows, 198 + 210MB So, am I doomed to either drop the foreign keys manually or use the table in a very un-Django way by defining saving bla_id x3 and skip using models.ForeignKey? I'd love to hear about some magical antidote / pg setting to fix this.

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• Joining Tables Based on Foreign Keys

  - by maestrojed

  I have a table that has a lot of fields that are foreign keys referencing a related table. I am writing a script in PHP that will do the db queries. When I query this table for its data I need to know the values associated with these keys not the key. How do most people go about this? A 101 way to do this would be to query this table for its data including the foreign keys and then query the related tables to get each key's value. This could be a lot of queries (~10). Question 1: I think I could write 1 query with a bunch of joins. Would that be better? This approach also requires the querying script to know which table fields are foreign keys. Since I have many tables like this but all with different fields, this means writing nice generic functions is hard. MySQL InnoDB tables allow for foreign constraints. I know the database has these set up correctly. Question 2: What about the idea of querying the table and identifying what the constraints are and then matching them up using whatever process I decide on from Question 1. I like this idea but never see it being used in code. Makes me think its not a good idea for some reason. I would use something like SHOW CREATE TABLE tbl_name; to find what constraints/relationships exist for that table. Thank you for any suggestions or advice.

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• Hibernate not saving foreign key, but with junit it's ok

  - by Leonardo

  Hi All, I have this strange problem. In a J2ee webapp with spring, smartgwt and hibernate, it happens that I have a class A wich has a set of class B, both of them mapped to table A and table B. I wrote a simple test case for testing the service manager which is supposed to do insert, update, delete and everything work as expected especially during insert. In the end I have one record in A and records in B with foreign key to A. But when I try to call the service from the web app, the entity in B are saved without a foreign key reference. I am sure that the service is the same. One thing I noticed is that enabling hibernate logging, seems that when the service is called from the application, one more update is made: insert A insert B update A update B update B (foreign key only) update A <--- ??? update B <--- ??? Instead, when junit test case is run, the update is as follows: insert A insert B update A update B update B (foreign key only) I suppose the latest update is what is causing the erroe, maybe it is overwriting values. Considering that the app is using spring, with the well known mechanism of DAO + Manager, where can I investigate to solve this issue ? Someone told me that the session is not closed, so hibernate would do one more update before release the objects by itself. I am pretty sure that all the configuration hbm, xml, and the rest are fine...but I maybe wrong. thanks

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• SubSonic isn't generating MySql foreign key tables

  - by keith

  I two tables within a MySql 5.1.34 database. When using SubSonic to generate the DAL, the foreign-key relationship doesn't get scripted, ie; I have no Parent.ChildCollection object. Looking inside the generated DAL Parent class shows the following; //no foreign key tables defined (0) I have tried SubSonic 2.1 and 2.2, and various MySql 5 versions. I must be doing something wrong procedurally - any help would be greatly appreciated. This has always just worked 'out-the-box' when using MS-SQL. TABLE `parent` ( `ParentId` INT(11) NOT NULL AUTO_INCREMENT, `SomeData` VARCHAR(25) DEFAULT NULL, PRIMARY KEY (`ParentId`) ) ENGINE=INNODB DEFAULT CHARSET=latin1; TABLE `child` ( `ChildId` INT(11) NOT NULL AUTO_INCREMENT, `ParentId` INT(11) NOT NULL, `SomeData` VARCHAR(25) DEFAULT NULL, PRIMARY KEY (`ChildId`), KEY `FK_child` (`ParentId`), CONSTRAINT `FK_child` FOREIGN KEY (`ParentId`) REFERENCES `parent` (`ParentId`) ) ENGINE=INNODB DEFAULT CHARSET=latin1;

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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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• Which MySQL Frontend shows foreign rows?

  - by Jeremy Rudd

  I once came across a MySQL Frontend app that displayed foreign linked rows within the parent row, if for instance the Events table has a foreign key to the Students table: Student ID Name DOB -- ---- --------- [+] 22 Bob 25-1-1984 [-] 21 Jane 25-1-1982 Event ID Student-ID Name Time -- ---------- ---- --------- 1 21 Event A 05:50 1 21 Event B 17:20 [+] 20 Jack 25-1-1980

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• Partitioning mySQL tables that has foreign keys?

  - by Industrial

  Hi! What would be an appropriate way to do this, since mySQL obviously doesnt enjoy this. To leave either partitioning or the foreign keys out from the database design would not seem like a good idea to me. I'll guess that there is a workaround for this? Update 03/24: http://opendba.blogspot.com/2008/10/mysql-partitioned-tables-with-trigger.html http://stackoverflow.com/questions/1537219/how-to-handle-foreign-key-while-partitioning Thanks!

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• Postgresql: Implicit lock acquisition from foreign-key constraint evaluation

  - by fennec

  So, I'm being confused about foreign key constraint handling in Postgresql. (version 8.4.4, for what it's worth). We've got a couple of tables, mildly anonymized below: device: (id, blah, blah, blah, blah, blah x 50)… primary key on id whooooole bunch of other junk device_foo: (id, device_id, left, right) Foreign key (device_id) references device(id) on delete cascade; primary key on id btree index on 'left' and 'right' So I set out with two database windows to run some queries. db1> begin; lock table device in exclusive mode; db2> begin; update device_foo set left = left + 1; The db2 connection blocks. It seems odd to me that an update of the 'left' column on device_stuff should be affected by activity on the device table. But it is. In fact, if I go back to db1: db1> select * from device_stuff for update; *** deadlock occurs *** The pgsql log has the following: blah blah blah deadlock blah. CONTEXT: SQL statement "SELECT 1 FROM ONLY "public"."device" x WHERE "id" OPERATOR(pg_catalog.=) $1 FOR SHARE OF X: update device_foo set left = left + 1; I suppose I've got two issues: the first is that I don't understand the precise mechanism by which this sort of locking occurs. I have got a couple of useful queries to query pg_locks to see what sort of locks a statement invokes, but I haven't been able to observe this particular sort of locking when I run the update device_foo command in isolation. (Perhaps I'm doing something wrong, though.) I also can't find any documentation on the lock acquisition behavior of foreign-key constraint checks. All I have is a log message. Am I to infer from this that any change to a row will acquire an update lock on all the tables which it's foreign-keyed against? The second issue is that I'd like to find some way to make it not happen like that. I'm ending up with occasional deadlocks in the actual application. I'd like to be able to run big update statements that impact all rows on device_foo without acquiring a big lock on the device table. (There's a lot of access going on in the device table, and it's kind of an expensive lock to get.)

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• MySQL foreign key creation with alter table command

  - by user313338

  I created some tables using MySQL Workbench, and then did forward ‘forward engineer’ to create scripts to create these tables. BUT, the scripts lead me to a number of problems. One of which involves the foreign keys. So I tried creating separate foreign key additions using alter table and I am still getting problems. The code is below (the set statements, drop/create statements I left in … though I don’t think they should matter for this): SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0; SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0; SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='TRADITIONAL'; DROP SCHEMA IF EXISTS `mydb` ; CREATE SCHEMA IF NOT EXISTS `mydb` DEFAULT CHARACTER SET latin1 COLLATE latin1_swedish_ci ; -- ----------------------------------------------------- -- Table `mydb`.`User` -- ----------------------------------------------------- DROP TABLE IF EXISTS `mydb`.`User` ; CREATE TABLE IF NOT EXISTS `mydb`.`User` ( `UserName` VARCHAR(35) NOT NULL , `Num_Accts` INT NOT NULL , `Password` VARCHAR(45) NULL , `Email` VARCHAR(45) NULL , `User_ID` INT NOT NULL AUTO_INCREMENT , PRIMARY KEY (`User_ID`) ) ENGINE = InnoDB; -- ----------------------------------------------------- -- Table `mydb`.`User_Space` -- ----------------------------------------------------- DROP TABLE IF EXISTS `mydb`.`User_Space` ; CREATE TABLE IF NOT EXISTS `mydb`.`User_Space` ( `User_UserName` VARCHAR(35) NOT NULL , `User_Space_ID` INT NOT NULL AUTO_INCREMENT , PRIMARY KEY (`User_Space_ID`), FOREIGN KEY (`User_UserName`) REFERENCES `mydb`.`User` (`UserName`) ON UPDATE CASCADE ON DELETE CASCADE) ENGINE = InnoDB; SET SQL_MODE=@OLD_SQL_MODE; SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS; SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS; The error this produces is: Error Code: 1005 Can't create table 'mydb.user_space' (errno: 150) Anybody know what the heck I’m doing wrong?? And anybody else have problems with the script generation done by mysql workbench? It’s a nice tool, but annoying that it pumps out scripts that don’t work for me. [As an fyi here’s the script it auto-generates: SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0; SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0; SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='TRADITIONAL'; DROP SCHEMA IF EXISTS `mydb` ; CREATE SCHEMA IF NOT EXISTS `mydb` DEFAULT CHARACTER SET latin1 COLLATE latin1_swedish_ci ; -- ----------------------------------------------------- -- Table `mydb`.`User` -- ----------------------------------------------------- DROP TABLE IF EXISTS `mydb`.`User` ; CREATE TABLE IF NOT EXISTS `mydb`.`User` ( `UserName` VARCHAR(35) NOT NULL , `Num_Accts` INT NOT NULL , `Password` VARCHAR(45) NULL , `Email` VARCHAR(45) NULL , `User_ID` INT NOT NULL AUTO_INCREMENT , PRIMARY KEY (`User_ID`) ) ENGINE = InnoDB; -- ----------------------------------------------------- -- Table `mydb`.`User_Space` -- ----------------------------------------------------- DROP TABLE IF EXISTS `mydb`.`User_Space` ; CREATE TABLE IF NOT EXISTS `mydb`.`User_Space` ( `User_Space_ID` INT NOT NULL AUTO_INCREMENT , PRIMARY KEY (`User_Space_ID`) , INDEX `User_ID` () , CONSTRAINT `User_ID` FOREIGN KEY () REFERENCES `mydb`.`User` () ON DELETE NO ACTION ON UPDATE NO ACTION) ENGINE = InnoDB; SET SQL_MODE=@OLD_SQL_MODE; SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS; SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS; ** Thanks!]

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• how to save related models with non-null foreign key

  - by Fortress

  I have a model called user which has_one email. I put the foreign key (NOT NULL) inside users table. Now I'm trying to save it in the following way: @email = Email.new(params[:email]) @email.user = User.new(params[:user]) @email.save This raises a db exception, because the foreign key constraint is not met (NULL is inserted into email_id). How can I elegantly solve this or is my data modeling wrong?

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• Phpmyadmin mysql foreign key help

  - by Alan

  Hey guys i'm using phpmyadmin (php & mysql) and i'm having alot of trouble linking the tables using foreign keys. I'm getting negative values for the field countyId (which is the foriegn key). However it is linking to my other table fine and it's cascading fine. So when I go to add data there will be a drop box for the CountyId and the vlaues will look something like this, " -1 1- " Here is my alter statement, ALTER TABLE Baronies ADD FOREIGN KEY (CountyId) REFERENCES Counties (CountyId) ON DELETE CASCADE

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• Foreign keys - temporarily bypass?

  - by Industrial

  Hi, I have just started to learn about the pros of foreign keys in database design (mySQL / innoDB) and I wonder if there's any way to temporarily bypass the foreign key when doing a specific delete query, to just delete in the parent table, and not from the linked child tables. Thanks

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• Foreign keys in django admin list display

  - by Olivier

  If a django model contains a foreign key field, and if that field is shown in list mode, then it shows up as text, instead of displaying a link to the foreign object. Is it possible to automatically display all foreign keys as links instead of flat text? (of course it is possible to do that on a field by field basis, but is there a general method?) Example: class Author(models.Model): ... class Post(models.Model): author = models.ForeignKey(Author) Now I choose a ModelAdmin such that the author shows up in list mode: class PostAdmin(admin.ModelAdmin): list_display = [..., 'author',...] Now in list mode, the author field will just use the __unicode__ method of the Author class to display the author. On the top of that I would like a link pointing to the url of the corresponding author in the admin site. Is that possible? Manual method: For the sake of completeness, I add the manual method. It would be to add a method author_link in the PostAdmin class: def author_link(self, item): return '<a href="../some/path/%d">%s</a>' % (item.id, unicode(item)) author_link.allow_tags = True That will work for that particular field but that is not what I want. I want a general method to achieve the same effect. (One of the problems is how to figure out automatically the path to an object in the django admin site.)

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• [Linq to SQL] Multiple foreign keys to the same table

  - by cdonner

  I have a reference table with all sorts of controlled value lookup data for gender, address type, contact type, etc. Many tables have multiple foreign keys to this reference table I also have many-to-many association tables that have two foreign keys to the same table. Unfortunately, when these tables are pulled into a Linq model and the DBML is generated, SQLMetal does not look at the names of the foreign key columns, or the names of the constraints, but only at the target table. So I end up with members called Reference1, Reference2, ... not very maintenance-friendly. Example: <Association Name="tb_reference_tb_account" Member="tb_reference" <====== ThisKey="shipping_preference_type_id" OtherKey="id" Type="tb_reference" IsForeignKey="true" /> <Association Name="tb_reference_tb_account1" Member="tb_reference1" <====== ThisKey="status_type_id" OtherKey="id" Type="tb_reference" IsForeignKey="true" /> I can go into the DBML and manually change the member names, of course, but this would mean I can no longer round-trip my database schema. This is not an option at the current stage of the model, which is still evolving. Splitting the reference table into n individual tables is also not desirable. I can probably write a script that runs against the XML after each generation and replaces the member name with something derived from ThisKey (since I adhere to a naming convention for these types of keys). Has anybody found a better solution to this problem?

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• SQL Server problems reading columns with a foreign key

  - by illdev

  I have a weird situation, where simple queries seem to never finish for instance SELECT top 100 ArticleID FROM Article WHERE ProductGroupID=379114 returns immediately SELECT top 1000 ArticleID FROM Article WHERE ProductGroupID=379114 never returns SELECT ArticleID FROM Article WHERE ProductGroupID=379114 never returns SELECT top 1000 ArticleID FROM Article returns immediately By 'returning' I mean 'in query analyzer the green check mark appears and it says "Query executed successfully"'. I sometimes get the rows painted to the grid in qa, but still the query goes on waiting for my client to time out - 'sometimes': SELECT ProductGroupID AS Product23_1_, ArticleID AS ArticleID1_, ArticleID AS ArticleID18_0_, Inventory_Name AS Inventory3_18_0_, Inventory_UnitOfMeasure AS Inventory4_18_0_, BusinessKey AS Business5_18_0_, Name AS Name18_0_, ServesPeople AS ServesPe7_18_0_, InStock AS InStock18_0_, Description AS Descript9_18_0_, Description2 AS Descrip10_18_0_, TechnicalData AS Technic11_18_0_, IsDiscontinued AS IsDisco12_18_0_, Release AS Release18_0_, Classifications AS Classif14_18_0_, DistributorName AS Distrib15_18_0_, DistributorProductCode AS Distrib16_18_0_, Options AS Options18_0_, IsPromoted AS IsPromoted18_0_, IsBulkyFreight AS IsBulky19_18_0_, IsBackOrderOnly AS IsBackO20_18_0_, Price AS Price18_0_, Weight AS Weight18_0_, ProductGroupID AS Product23_18_0_, ConversationID AS Convers24_18_0_, DistributorID AS Distrib25_18_0_, type AS Type18_0_ FROM Article AS articles0_ WHERE (IsDiscontinued = '0') AND (ProductGroupID = 379121) shows this behavior. I have no idea what is going on. Probably select is broken ;) I got a foreign key on ProductGroups ALTER TABLE [dbo].[Article] WITH CHECK ADD CONSTRAINT [FK_ProductGroup_Articles] FOREIGN KEY([ProductGroupID]) REFERENCES [dbo].[ProductGroup] ([ProductGroupID]) GO ALTER TABLE [dbo].[Article] CHECK CONSTRAINT [FK_ProductGroup_Articles] there are some 6000 rows and IsDiscontinued is a bit, not null, but leaving this condition out does not change the outcome. Anyone can tell me how to handle such a situation? More info, anyone? Additional Info: this does not seem to be restricted to this Foreign Key, but all/some referencing this entity.

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• Fluent composite foreign key mapping

  - by Fionn

  Hi, I wonder if this is possible to map the following with fluent nhibernate: A document table and a document_revision table will be the target tables. The document_revision table should have a composite unique key consisting of the document_id and the revision number (where the document_id is also the foreign key to the document table). class Document { Guid Id; //other members omitted } class DocumentRevision { Guid document_id; //Part one of the primary key and also foreign key to Document.Id int revision; //Part two of the primary key //other members omitted }

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• Create automatically table that is composed by its primery key and 2 other foreign keys

  - by user210481

  I have table A with a primary id, a table B with a primary key id also and another table C with a primary key id and rows Aid and Bid where Aid and Bid are foreign keys of C and the primary keys of A and B respectively. One way of populating these DB would be populating table A, table B and table C separately. I would like to know if there is a more clever way of doing it, where I could populate A first and at the same time I populate B, I can indicate that an entry in C should be also created. Any idea and suggestion on how to populate them is welcome. I'm trying to take advantage of the foreign keys structure Thanks

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• Manage Foreign key and Drop downlist for optional field in .NET

  - by Brij

  What is the best way to handle following situation? A dropdown(for master table) is optional in a particular form. But, In database table the field is constrained with foreign key. If user don't select from dropdown then It creates problem because of foreign key. One solution is to create default option in master table and use it in case of blank selection. but in dropdown, we need to handle this to show on top. Is it perfect solution? Is there any other optimized solution for this? Thanks

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• T-SQL foreign key check constraint

  - by PaN1C_Showt1Me

  When you create a foreign key constraint in a table and you create the script in MS SQL Management Studio, it looks like this. ALTER TABLE T1 WITH CHECK ADD CONSTRAINT FK_T1 FOREIGN KEY(project_id) REFERENCES T2 (project_id) GO ALTER TABLE T1 CHECK CONSTRAINT FK_T1 GO What I don't understand is what purpose has the second alter with check constraint. Isn't creating the FK constraint enough? Do you have to add the check constraint to assure reference integrity ? Another question: how would it look like then when you'd write it directly in the column definition? CREATE TABLE T1 ( my_column INT NOT NULL CONSTRAINT FK_T1 REFERENCES T2(my_column) ) Isn't this enough?

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• linq to sql using foreign keys returning iqueryable(of myEntity]

  - by Gern Blandston

  I'm trying to use Linq to SQL to return an IQueryable(of Project) when using foreign key relationships. Using the below schema, I want to be able to pass in a UserId and get all the projects created for the company the user is associated with. DB tables: Projects Projid ProjCreator FK (UserId from UserInfo table) Companyid FK (CompanyID from Companies table) UserInfo UserID PK Companyid FK Companies CompanyId PK Description I can get the iqueryable(of project) when simply getting the ProjectCreator with this: Return (From p In db.Projects _ Where p.ProjectCreator = Me.UserId) But I'm having trouble getting the syntax to get a iqueryable(of projects) when using foreign keys. Below gives me an IQueryable(of anonymous) but I can't seem to convince it to give me an IQueryable(of project) even if I try to cast it: Dim retval = (From p In db.Projects _ Join c In db.Companies On p.CompanyId Equals c.CompanyId _ Join u In db.UserInfos On u.CompanyId Equals c.CompanyId _ Where u.Login = UserId)

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• Multiple foreign keys from one table linking to single primary key in second table

  - by croker10

  Hi all, I have a database with three tables, a household table, an adults table and a users table. The Household table contains two foreign keys, iAdult1ID and iAdult2ID. The Users table has a iUserID primary key and the Adult table has a corresponding iUserID foreign key. One of the columns in the Users table is strUsername, an e-mail address. I am trying to write a query that will allow me to search for an e-mail address for either adult that has a relation to the household. So I have two questions, assuming that all the values are not null, how can I do this? And two, in reality, iAdult2ID can be null, is it still possible to write a query to do this? Thanks for your help. Let me know if you need any more information.

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• mysql foreign key problem.

  - by JP19

  Hi, What is wrong with the foreign key addition here: mysql> create table notes ( id int (11) NOT NULL auto_increment PRIMARY KEY, note_type_id smallint(5) NOT NULL, data TEXT NOT NULL, created_date datetime NOT NULL, modified_date timestamp NOT NULL on update now()) Engine=InnoDB; Query OK, 0 rows affected (0.08 sec) mysql> create table notetypes ( id smallint (5) NOT NULL auto_increment PRIMARY KEY, type varchar(255) NOT NULL UNIQUE) Engine=InnoDB; Query OK, 0 rows affected (0.00 sec) mysql> alter table `notes` add constraint foreign key(`note_type_id`) references `notetypes`.`id` on update cascade on delete restrict; ERROR 1005 (HY000): Can't create table './admin/#sql-43e_b762.frm' (errno: 150) Thanks JP

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• PostgreSQL: How to index all foreign keys?

  - by biggusjimmus

  I am working with a large PostgreSQL database, and I are trying to tune it to get more performance. Our queries and updates seem to be doing a lot of lookups using foreign keys. What I would like is a relatively simple way to add Indexes to all of our foreign keys without having to go through every table (~140) and doing it manually. In researching this, I've come to find that there is no way to have Postgres do this for you automatically (like MySQL does), but I would be happy to hear otherwise there, too.

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