Constraints and data defaults

You're now going to practice creating a table with some constraints! Often, you'll need to make sure that a column is unique, nullable, a positive value, or related to a column in another table. This is where constraints come in.

As Jason showed you in the video, in addition to constraints, you can also set a default value for the column if no data is passed to it via the default keyword on the column.

Deze oefening maakt deel uit van de cursus

Introduction to Databases in Python

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Oefeninstructies

Table, Column, String, Integer, Float, Boolean are already imported from sqlalchemy.
Build a new table called data with a unique name (String), count (Integer) defaulted to 1, amount (Float), and valid (Boolean) defaulted to False.
Submit the answer to create the table in the database and to print the table details for data.

Praktische interactieve oefening

Probeer deze oefening eens door deze voorbeeldcode in te vullen.

# Import Table, Column, String, Integer, Float, Boolean from sqlalchemy
from sqlalchemy import Table, Column, String, Integer, Float, Boolean

# Define a new table with a name, count, amount, and valid column: data
data = Table('data', metadata,
             Column('name', String(255), unique=____),
             Column('count', Integer(), default=____),
             Column('amount', Float()),
             Column('valid', Boolean(), default=____)
)

# Use the metadata to create the table
metadata.create_all(engine)

# Print the table details
print(repr(metadata.tables['data']))

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