Dynamic join sqlalchemy

Question

I want to dynamically join a certain number of tables from a list containing table names, for example if my list contains two elements like this :

tables_to_join = ['table1','table2']

Then I would like to have a left join between those two tables in the query.

table1 LEFT JOIN table2 on table1.id = table2.id

And if the table only contains one element, then there will be no need to do a join.

How can I do this with SQLAlchemy please?

I guess I should do something like this :

test_query = session.query(my_table).join(tables_to_join)

But then how can I manage the case where there will be no need to join (if table_to_join contains only one element) ?

Any help would be awesome!

Can't you just check the length of the tables_to_join, and then stick the .join(tables_to_join) part in an if loop? Or did I miss something here. — Burhan Khalid
– Burhan Khalid, Commented Jul 4, 2013 at 12:04

yonili · Accepted Answer · 2013-07-04 13:13:37Z

1

tables_to_join = [..]

if (len(tables_to_join) > 1):
    query = session.query(eval(tables_to_join[0]))

    for table in tables_to_join[1:]:
        query = query.join(eval(table))

answered Jul 4, 2013 at 13:13

yonili

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