["python","sql","database","sqlalchemy"]
Select NULL Values in SQLAlchemy

Here's my (PostgreSQL) table -- test=> create table people (name varchar primary key, marriage_status varchar) ; test=> insert into people values ('Ken', 'married'); test=> insert into people values ('May', 'single'); test=> insert into people values ('Joe', NULL); I want to select all people that are not known to be married, i.e., including those with NULL marriage_status. This does not work -- test=> select * from people where marriage_status != 'married' ; name | marriage_status ------+----------------- May | single (1 row) Of course this does -- test=> select * from people where marriage_status != 'married' or marriage_status is NULL ; name | marriage_status ------+----------------- May | single Joe | The problem is that I'm accessing it from SQLAlchemy with -- ...filter(or_(people.marriage_status!='married', people.marriage_status is None)) which gets translated to -- SELECT people.name as name, people.marriage_status as marriage_status FROM people WHERE people.marriage_status != %(status_1)s OR False sqlalchemy.engine.base.Engine.... {'status_1': 'married'} And does not work -- test=> select * from people where marriage_status != 'married' or False; name | marriage_status ------+----------------- May | single (1 row) neither does -- test=> select * from people where marriage_status != 'married' or NULL; name | marriage_status ------+----------------- May | single (1 row) How should I select NULL values through SQLAlchemy?
For SQLAlchemy 0.7.9 and newer Please use the answer from @jsnow. !!! For SQLAlchemy 0.7.8 and older (as indicated by @augurar): Because sqlalchemy uses magic methods (operator overloading) to create SQL constructs, it can only handle operator such as != or ==, but is not able to work with is (which is a very valid Python construct). Therefore, to make it work with sqlalchemy, you should use: ...filter(or_(people.marriage_status!='married', people.marriage_status == None)) , basically replace the is None with == None. In this case your query will be translated properly to the following SQL: SELECT people.name AS people_name, people.marriage_status AS people_marriage_status FROM people WHERE people.marriage_status IS NULL OR people.marriage_status != ? See IS NULL in the documentation.