I have a Django web-server configured to use SQLite.
In a many-to-many relationship (with extra fields), Django forces me to use the relationship model to establish a relationship between two objects. But I'm able to create a relationship between objects, that don't yet exist in the related tables.
For e.g:
I have table1 and table2 which are related via table12.
In table1, there is just one object called A.
In table2, there is just one object called X.
I can create a record in table12 that depict a relationship between A & Y; even though Y doesn't exist in table2.
My relationship model has marked the foreign keys appropriately.
SQLite does not enforce foreign key constraints by default (mostly to be backward compatible).
To enable it, you have to execute
PRAGMA foreign_keys = 1
after you connected to the database.
See the manual about PRAGMA foreign_keys for more details.
来源：https://stackoverflow.com/questions/17213454/does-sqlite-support-referential-integrity