Filtering for empty string in SQLAlchemy + Oracle

Question

I have a weird problem with querying for strings using Oracle 11g backend for SQLAlchemy. First, class definition (for Oracle, for Postgres it is the same minus Sequence):

class Item(Base):
    __tablename__ = 'item'
    id = Column(Integer, Sequence('id_seq'), primary_key=True)
    ...
    review = Column(Unicode(2000), index=True)

Basic querying works without a problem with Postgres backend:

In [1]: len(DBSession.query(Item).filter(Item.review != '').limit(100).all())
Out[1]: 100

However, with Oracle 11g:

In [31]: len(DBSession.query(Item).filter(Item.review != '').limit(100).all())
Out[31]: 0

Filtering by empty Unicode string does not work either in Oracle:

In [32]: len(DBSession.query(Item).filter(Item.review != u'').limit(100).all())
Out[32]: 0

Why something so basic does not work with Oracle? And how can I fix that?

Community · Accepted Answer · 2017-05-23 12:24:03Z

2

This has nothing to do with SQLAlchemy. Oracle treats empty string == null.

See: Oracle treats an empty string as null

edited May 23, 2017 at 12:24

CommunityBot

11 silver badge

answered Jun 9, 2016 at 19:27

MikeGeezee

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