foreign-keys

In SQL Server 2008 and given TableA(A_ID, A_Data) TableB(B_ID, B_Data) ViewC(A_or_B_ID, A_or_B_Data) is it possible to define TableZ(A_or_B_ID, Z_Data) such that Z.A_or_B_ID column is constrained to the values found in ViewC ? Can this be done with a foreign key against the view? You can't reference a view in a foreign key. In older SQL Server editions foreign keys were possible only through triggers. You can mimic a custom foreign key by creating an Insert trigger which checks whether the inserted value appears in one of the relevant tables as well. If you really need A_or_B_ID in TableZ, you

Essentially, I am having the same issue as this guy, minus the table prefix. Because I have no table prefix, his fix does not work. http://forums.laravel.com/viewtopic.php?id=972 I am trying to build a table using Laravel's Schema Builder like this: Schema::create('lessons', function($table) { $table->increments('id'); $table->string('title')->nullable(); $table->string('summary')->nullable(); $table->timestamps(); }); Schema::create('tutorials', function($table) { $table->increments('id'); $table->integer('author'); $table->integer('lesson'); $table->string('title')->nullable(); $table-

I'm currently designing a database structure for our team's project. I have this very question in mind currently: Is it possible to have a foreign key act as a primary key on another table? Here are some of the tables of our system's database design: user_accounts students guidance_counselors What I wanted to happen is that the user_accounts table should contain the IDs (supposedly the login credential to the system) and passwords of both the student users and guidance counselor users. In short, the primary keys of both the students and guidance_counselors table are also the foreign key from

When I run a mysqldump command on my database and then try to import it, it fails as it attempts to create the tables alphabetically, even though they may have a foreign key that references a table later in the file. There doesn't appear to be anything in the documentation and I've found answers like this that say to update the file after it's created to include: set FOREIGN_KEY_CHECKS = 0; ...original mysqldump file contents... set FOREIGN_KEY_CHECKS = 1; Is there no way to automatically set those lines or export the tables in the necessary order (without having to manually specify all table

I have a table that has two foreign keys to two different tables with both foreign keys sharing one column : CREATE TABLE ZipAreas ( country_code CHAR(2) NOT NULL, zip_code VARCHAR(10) NOT NULL, state_code VARCHAR(5) NOT NULL, city_name VARCHAR(100) NOT NULL, PRIMARY KEY (country_code, zip_code, state_code, city_name), FOREIGN KEY (country_code, zip_code) REFERENCES Zips (country_code, code), FOREIGN KEY (country_code, state_code, city_name) REFERENCES Cities (country_code, state_code, name) ) As you can see, there are two FKs sharing country_code (coincidentally referencing the same column at

I have the same problem as in the following post . So I am wondering, why doesn't Rails support generating foreign keys by default? Isn't it necessary? Or are we supposed to do it manually? Database constraints aren't required any more than wearing seat-belts are required in your car. You can drive around all you like and everything will work great until a problem arrives. The seat-belt (constraints) keep you (the data) safe. So it's highly recommended that you create constraints to enforce data-integrity at the database level, because it's highly likely that 1) You will interact with the

it is written in every book that foreign keys are actually primary key in some other table but can we have a foreign key which is not primary key in any other table Yes - you can have a foreign key that references a unique index in another table. CREATE UNIQUE INDEX UX01_YourTable ON dbo.YourTable(SomeUniqueColumn) ALTER TABLE dbo.YourChildTable ADD CONSTRAINT FK_ChildTable_Table FOREIGN KEY(YourFKColumn) REFERENCES dbo.YourTable(SomeUniqueColumn) By definition a foreign key must reference a candidate key of some table. It doesn't necessarily have to be the primary key. As a matter of detail