OK, after 2 days of trying and searching creating a post in the google groups leads to rephrasing the problem. And this often leads to finding the solution:
I managed to do it this way: MyTable.query.with_entities(MyTable.columnB).distinct().all() Problem solved... Am Sonntag, 8. Oktober 2017 09:27:49 UTC+2 schrieb Cornelius Kölbel: > > Hi, > > I have a table with many columns (columnA, columnB, columnC) and I want to > know, how many different entries in columnB are. > I would do such an SQL query: > > select distinct columnB from myTable; > > I see there is also ``distinct()`` in SQL Alchemy. > > However - I am using Class defined ORM like this: > > class MyTable(db.Model): > __tablename__ = "myTable" > columnA = db.Column(...) > columnB = db.Column(...) > columnC = db.Column(...) > > Thus, I am querying like this: > > > MyTable.query.all() > > The problem seems to be that I was not able to figure out a way to reduce > the columns, e.g. when I add a ``distinct`` > > > MyTable.query.distinct.all() > > The distinct function will always use **all** columns. > I also tried ``load_only`` with no success. > > I understand, I could define a class, containing only the required column, > then I am told, I should just some ``extend_existing``. > > What is the required way to use ``distinct`` in a class based query? > > Thanks a lot > Cornelius > -- SQLAlchemy - The Python SQL Toolkit and Object Relational Mapper http://www.sqlalchemy.org/ To post example code, please provide an MCVE: Minimal, Complete, and Verifiable Example. See http://stackoverflow.com/help/mcve for a full description. --- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at https://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
