foreign-keys

I have a strange problem with mysql. I am trying to alter a table's column which is a primary key and has an auto_increment constraint defined on it. This is also a foreign key reference for multiple other tables. I need to change the length of this column in both , parent and all children. set foreign_key_checks=0; alter table Parent modify Identifier smallint(10) unsigned; alter table Child_1 modify FK_Identifier smallint(10) unsigned; alter table Child_2 modify FK_Identifier smallint(10) unsigned; alter table Child_3 modify FK_Identifier smallint(10) unsigned; alter table Child_4 modify FK

If I define a Customer and Order model in which a Customer "has many" Orders and the Order "belongs to" the Customer , in Rails we talk about Order having a foreign key to the Customer through customer_id but we don't mean that this is enforced in the database. Because Rails does not define this as a database-level constraint, there is a risk of your data's integrity being violated, perhaps outside the application (or inside if you receive simultaneous requests?), unless you enforce the constraint in the database manually. Why does Rails not define the foreign key at the database level or is

I am not an expert in sql / sqlite.. suppose we have two tables: CREATE TABLE child ( id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT, ); CREATE TABLE MyTableB( dog TEXT, FOREIGN KEY(dogList) REFERENCES child(id) ); how will the INSERT? is correct my createTable operations? I would like to have: a child can have more than one dog a dog can have more children EDIT What if I wanted all the children and for each child a list of dogs associated with that child? Many-To-Many In order to support a child having zero or more dogs and a dog belonging to zero or more children, your database table

Would the following SQL statement automatically create an index on Table1.Table1Column, or must one be explicitly created? Database engine is SQL Server 2000 CREATE TABLE [Table1] ( . . . CONSTRAINT [FK_Table1_Table2] FOREIGN KEY ( [Table1Column] ) REFERENCES [Table2] ( [Table2ID] ) ) jons911 SQL Server will not automatically create an index on a foreign key. Also from MSDN: A FOREIGN KEY constraint does not have to be linked only to a PRIMARY KEY constraint in another table; it can also be defined to reference the columns of a UNIQUE constraint in another table. A FOREIGN KEY constraint can

Is there a way to persist an enum to the DB using NHibernate? That is have a table of both the code and the name of each value in the enum. I want to keep the enum without an entity, but still have a foreign key (the int representation of the enum) from all other referencing entities to the enum's table. Why are you guys over complicating this? It is really simple. The mapping looks like this: <property name="OrganizationType"></property> The model property looks like this: public virtual OrganizationTypes OrganizationType { get; set; } The Enum looks like this: public enum OrganizationTypes {

How do I design a scheme such this in MongoDB? I think there are no foreign keys! You may be interested in using a ORM like Mongoid or MongoMapper. http://mongoid.org/docs/relations/referenced/1-n.html In a NoSQL database like MongoDB there are not 'tables' but documents. Documents are grouped inside Collections. You can have any kind of document – with any kind of data – in a single collection. Basically, in a NoSQL database it is up to you to decide how to organise the data and its relations, if there are any. What Mongoid and MongoMapper do is to provide you with convenient methods to set

I don't have much experience with SQLAlchemy and I have a problem, which I can't solve. I tried searching and I tried a lot of code. This is my Class (reduced to the most significant code): class Patient(Base): __tablename__ = 'patients' id = Column(Integer, primary_key=True, nullable=False) mother_id = Column(Integer, ForeignKey('patients.id'), index=True) mother = relationship('Patient', primaryjoin='Patient.id==Patient.mother_id', remote_side='Patient.id', uselist=False) phenoscore = Column(Float) and I would like to query all patients, whose mother's phenoscore is (for example) == 10 As