Automatic joins with an established relationship
If you have two tables that already have an established relationship, you can automatically use that relationship by just adding the columns we want from each table to the select statement. Recall that Jason constructed the following query:
stmt = select([census.columns.pop2008, state_fact.columns.abbreviation])
in order to join the census and state_fact tables and select the pop2008 column from the first and the abbreviation column from the second. In this case, the census and state_fact tables had a pre-defined relationship: the state column of the former corresponded to the name column of the latter.
In this exercise, you'll use the same predefined relationship to select the pop2000 and abbreviation columns!
Diese Übung ist Teil des Kurses
Introduction to Databases in Python
Anleitung zur Übung
- Build a statement to join the
censusandstate_facttables and select thepop2000column from the first and theabbreviationcolumn from the second. - Execute the statement to get the first result and save it as
result. - Submit the answer to loop over the keys of the result object, and print the key and value for each!
Interaktive Übung
Versuche dich an dieser Übung, indem du diesen Beispielcode vervollständigst.
# Build a statement to join census and state_fact tables: stmt
stmt = select([____, ____])
# Execute the statement and get the first result: result
result = connection.execute(____).first()
# Loop over the keys in the result object and print the key and value
for key in result.keys():
print(key, getattr(result, key))