How do I set the server_default for a MySQL SET in SQLAlchemy?

Question

I've got a MySQL set column I'm describing using sqlalchemy.dialects.mysql.SET and I want to set the server_default arg to a set containing two values. I'm looking for something like this:

from sqlalchemy.dialects.mysql import SET
class MyTable(Model):
    letters = Column(SET('a', 'b', 'c', 'd', 'e'), server_default=['a','b'])

If I try something as simple as the above I get:

Argument 'arg' is expected to be one of type '<class 'str'>' or '<class 'sqlalchemy.sql.elements.ClauseElement'>' or '<class 'sqlalchemy.sql.elements.TextClause'>', got '<class 'list'>'

Is there somewhere I can find a list of ClauseElements I can use?

Answer 1

Perhaps the best reference for different ClauseElement s is "Column Elements and Expressions" .

From reading "The SET Type" it seems that a common way to pass values to a SET column in MySQL is to use a (SQL) string literal with comma separated values. One way then would be to use SQLAlchemy's literal() , which produces a suitable bind parameter. You would then pass a literal string like this:

from sqlalchemy import literal
from sqlalchemy.dialects.mysql import SET

class MyTable(Model):

    letters = Column(SET('a', 'b', 'c', 'd', 'e'), server_default=literal('a,b'))