filters1.py

This example shows how to use the NotEmpty filter for a Detail column, which leads to a nested SELECT in the SQL code.

Source code:

from lino.apps.contacts.contacts_demo import startup
from lino.apps.contacts.contacts_tables import Nation
from lino.adamo.filters import NotEmpty

dbc = startup() # big=True)
        
qry=dbc.query(Nation,"id name cities")
qry.addColFilter('cities',NotEmpty)
qry.show(columnWidths="2 15 20")

print
print qry.getSqlSelect()

del dbc, qry

Output:

Nations where 'cities' not empty
================================
id|name           |cities              
--+---------------+--------------------
ee|Estonia        |10 Cities           
be|Belgium        |9 Cities            
de|Germany        |7 Cities            

SELECT id, name_en FROM Nations WHERE EXISTS (SELECT * FROM Cities WHERE nation_id=Nations.id)

Refering articles:

• filters1.py needs DetailColumn (code changes 04.03.06) — I noticed that filters1.py and filters2.py show a rather serious problem of the new paradigm for handling details. It sets a filter on a detail column. But I thought such columns to disappear. How can I convert filters1.py to the new paradigm? Answer: DetailColumn remains.
• filters on subqueries: first success (06.05.05) — Uff! Filtering on subqueries (see examples filters1.py and filters2.py) works finally. Soon I will use this for Keeper.

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