Selecting rows
SQL WHERE clauses return records whose values meet the given criteria. Passing such a query to read_sql() results in a dataframe loaded with only records we are interested in, so there is less filtering to do later on.
The hpd311calls table in data.db has data on calls about various housing issues, from maintenance problems to information requests. In this exercise, you'll use SQL to focus on calls about safety.
pandas has been loaded as pd, and a database engine, engine, has been created for data.db.
Diese Übung ist Teil des Kurses
Streamlined Data Ingestion with pandas
Anleitung zur Übung
- Create a query that selects all columns of records in
hpd311callsthat have'SAFETY'as theircomplaint_type. - Use
read_sql()to query the database and assign the result to the variablesafety_calls. - Run the last section of code to create a graph of safety call counts in each borough.
Interaktive Übung
Versuche dich an dieser Übung, indem du diesen Beispielcode vervollständigst.
# Create query to get hpd311calls records about safety
query = """
____ *
____ hpd311calls
____ ____;
"""
# Query the database and assign result to safety_calls
safety_calls = ____
# Graph the number of safety calls by borough
call_counts = safety_calls.groupby('borough').unique_key.count()
call_counts.plot.barh()
plt.show()