Top "Foreign-key-relationship" questions

Foreign keys are a data integrity feature of relational (and SQL) databases.

Defining multiple Foreign Key for the Same table in Entity Framework Code First

I have two entities in my MVC application and I populated the database with Entity Framework 6 Code First approach. There …

asp.net-mvc entity-framework ef-code-first foreign-keys foreign-key-relationship
How to duplicate schemas in PostgreSQL

I have a database with schema public and schema_A. I need to create a new schema schema_b with …

postgresql database-schema foreign-key-relationship postgresql-9.1
SQLite Foreign Key

I'm following the instructions from the SQLite documentation at http://www.sqlite.org/foreignkeys.html however my attempt to add …

android sql sqlite foreign-key-relationship create-table
Why can you not have a foreign key in a polymorphic association?

Why can you not have a foreign key in a polymorphic association, such as the one represented below as a …

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Add a Foreign Key in PgAdmin

I have studidtemplates table below: template_id is the primary_key I want to create a new table referencing template_…

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Postgres: left join with order by and limit 1

I have the situation: Table1 has a list of companies. Table2 has a list of addresses. Table3 is a N …

postgresql sql-order-by left-join foreign-key-relationship duplicate-removal
unable to drop the foreign key

I would like to drop the foreign key in my table but been into this error message mysql> alter …

mysql foreign-keys foreign-key-relationship mysql-error-1025
SQL Sub queries in check constraint

Can I make SQL sub queries in Check constraint ? I've a post table with columns id, owner I've another table …

postgresql foreign-key-relationship plpgsql check-constraints
"Invalid Index n for this SqlParameterCollection with Count=n" OR "foreign key cannot be null"

I have been successfully using NHibernate for quite some time now and have been able to solve a lot of …

nhibernate mapping foreign-key-relationship
Whats the difference between a OneToOne, ManyToMany, and a ForeignKey Field in Django?

I'm having a little difficulty getting my head around relationships in Django models. Could someone explain what the difference is …

python django many-to-many foreign-key-relationship one-to-one