SQLAlchemy中的外键约束

Question

I'm using the ORM side of SQLAlchemy, and I've defined one of my columns to have a foreign key relation to another model, using:

Base = declarative_base()
class Model1(Base):
    __tablename__ = 'm1'
    Name = Column(String, primary_key = True)
    info = Column(String)

class Model2(Base):
    __tablename__ = 'm2'
    Name = Column(String, primary_key = True)
    info = Column(String)
    other_model = Column(String, ForeignKey('m1.Name'))

However, it doesn't seem to matter what I put in the other_model attribute, it seems more than happy to commit it to the database, even if there is no Model1 instance that has that Name .

Answer 1

It looks like the answer was in the database I was using (SQLite), not SQLAlchemy. SQLite versions <3.6.1 (AFAIK) do not support foreign key constraints.

The answer is therefore very similar to this answer on foreign keys and SQLAlchemy .

As I'm using Windows, I was able to go to the pysqlite2 page , the packaged installers have version 3.7.6.2 sqlite, and then and the final implementation was aided by this SQLAlchemy page on sqlite engines and dialects . This SO question is also relevant with regards to the upgrade process.

Finally, the SQLite engine is a bit temperamental when deciding whether or not to enforce the foreign key constraint, and this SO question is quite useful in forcing the foreign key enforcement.