I know that in MySQL, UNIQUE constraits don't treat NULL values as equal. So if I have a unique constraint on ColumnX, then two separate rows can have values of NULL for ColumnX and this wouldn't violate the constraint. How can I work around this? I can't just set the value to an arbitrary constant that I can flag, because ColumnX in m...
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 ca...
Here is my problem: I have 2 tables: 1.WORKER, with coloumns |ID|OTHER_STAF| , where ID is primary key, and 2.FIRM, with coloumns |FPK|ID|SOMETHING_ELSE| , where combination FPK and ID make primary key, and also ID is a foreign key referenced to WORKER.ID (not null, and must have same value as in WORKER). I want to make stored proced...
I have been working on it for quite a while, but still can't figure out what's wrong with my code. Each Service has multiple profiles, but each profile only has one Service. Service { Long service_id; // primary key ... getter/setter } Profile { Long profile_id; // primary key Long service_id; // foreign key ... getter and setter } i...
My guess would be that a foreign key reference is set to RESTRICT by default. But, is there any standard for this? Is the default equal on any database type? Or should these values be defined in all statements just to be sure? ...
Hey! I´m using linq to sql and I have a lot of tables with foreign keys leading to the UserId. Is it possible to have some of these foreign tables cleaned upon deletion. For example I want the users profile (other table) to be deleted automatically with the user but not the users forum posts. Is this possible or do I have to handle ...
Hi! Since foreign keys are not supported by partitioned mySQL databases for the moment, I would like to hear some pro's and con's for a read-heavy application that will handle around 1-400 000 rows per table. Unfortunately, I dont have enough experience yet in this area to make the conclusion by myself... Thanks a lot! References: h...
Hi, This is my model. class User{ @CollectionOfElements @JoinTable(name = "user_type", joinColumns = @JoinColumn(name = "user_id")) @Column(name = "type", nullable = false) private List<String> types = new ArrayList<String>(); } You can imagin there would be a table called "user_type", which has two columns, one ...
I have a relatively simple subset of tables in my database for tracking something called sessions. These are academic sessions (think offerings of a particular program). The tables to represent a sessions information are: sessions session_terms session_subjects session_mark_item_info session_marks All of these tabl...
Hello! I have two models related one-to many: class Person(models.Model): name = models.CharField(max_length=255); surname = models.CharField(max_length=255); age = models.IntegerField(); class Dog(models.Model): name = models.CharField(max_length=255); owner = models.ForeignKey('Person...
Hi everyone! Doing my first tryouts with foreign keys in a mySQL database and are trying to do a insert, that fails for this reason: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails Does this mean that foreign keys restrict INSERTS as well as DELETES and/or UPDATES on each table that...
Hello, I am working on a database schema, and am trying to make some decisions about table names. I like at least somewhat descriptive names, but then when I use suggested foreign key naming conventions, the result seems to get ridiculous. Consider this example: Suppose I have table session_subject_mark_item_info And it has a forei...
I have two tables: tracks and waypoints, a track can have many waypoints, but a waypoint is assigned to only 1 track. In the way points table I have a column called "trackidfk" which inserts the track_ID once a track is made, however I have not setup Foreign Key constraints on this column. When I delete a track I want to delete the as...
Hello again, I have a table (session_comments) with the following fields structure: student_id (foreign key to students table) session_id (foreign key to sessions table) session_subject_ID (foreign key to session_subjects table) user_id (foreign key to users table) comment_date_time comment Now, the combination of student_id, session...
Table A has a computed field called Computed1. It's persisted and not null. Also, it always computes to an expression which is char(50). It's also unique and has a unique key constraint on it. Table B has a field RefersToComputed1, which should refer to a valid Computed1 value. Trying to create a foreign key constraint on B's RefersT...
I am writing a new app with Rails so I have an id column on every table. What is the best practice for enforcing domain constraints using foreign keys? I'll outline my thoughts and frustration. Here's what I would imagine as "The Rails Way". It's what I started with. Companies: id: integer, serial company_code: char, unique, no...
It is causing so much trouble in terms of development just by letting database enforcing foreign key. Especially during unit test I can’t drop table due to foreign key constrains, I need to create table in such an order that foreign key constrain warning won’t get triggered. In reality I don’t see too much point of letting database enfor...
I have the following tables: user (userid int [pk], name varchar(50)) action (actionid int [pk], description nvarchar(50)) being referenced by another table that captures the relationship: <user1> <action>'s <user2>. I did this with the following table: userAction (userActionId int [pk], actionid int [fk: action.actionid], **us...
I am trying to add a foreign key constraint via sqlyog, and getting this error, although I am only select one source and one reference columns please select equal number of source and reference Does anyone knows what it means in this case? Note that I do have an equal number of source and reference columns... ...
Hello, I'm new to Ruby on Rails (I know Ruby just decently though) and looking at the Migration tools, it sounds really awesome. Database schemas can finally (easily) go in source control. Now my problem with it. When using Postgres as the database, it does not setup foreign keys. I would like the benefits of foreign keys in my schema ...