Joining on relations
You've used the following diagram in the previous exercise:
You've learned that you can use the read_sql() function from pandas to query the database. The real power of SQL is the ability to join information from multiple tables quickly. You do this by using the JOIN statement.
When joining two or more tables, pandas puts all the columns of the query result into a DataFrame.
Deze oefening maakt deel uit van de cursus
Introduction to Data Engineering
Oefeninstructies
- Complete the
SELECTstatement, so it joins the"Customer"with the"Order"table. - Print the
idcolumn ofdata. What do you see?
Praktische interactieve oefening
Probeer deze oefening eens door deze voorbeeldcode in te vullen.
# Complete the SELECT statement
data = pd.read_sql("""
SELECT * FROM "Customer"
INNER JOIN "____"
ON "Order"."____"="Customer"."____"
""", db_engine)
# Show the id column of data
print(data.____)