Column types and constraints in Flask - Cheat Sheet & Quick Revision

Recall & Review

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What is a column type in Flask-SQLAlchemy?

A column type defines the kind of data a column can hold, like Integer, String, or DateTime. It tells the database what type of information to expect.

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What does the nullable=False constraint do in a column?

It means the column cannot have empty or NULL values. Every row must have a value for that column.

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How do you set a column to be a primary key in Flask-SQLAlchemy?

You add primary_key=True to the column definition. This makes the column unique and identifies each row.

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What is the purpose of the unique=True constraint?

It ensures that all values in the column are different. No two rows can have the same value in that column.

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Name three common column types used in Flask-SQLAlchemy.

Common types include Integer for numbers, String for text, and DateTime for date and time values.

Which column type would you use to store a person's name in Flask-SQLAlchemy?

A String

B Integer

C Boolean

D DateTime

Names are text, so the String type is the right choice.

What does primary_key=True do in a column definition?

A Allows NULL values

B Sets a default value

C Makes the column optional

D Marks the column as unique and identifies each row

Primary key uniquely identifies each row and cannot be NULL.

If you want to make sure no two users have the same email, which constraint should you use?

A nullable=False

B unique=True

C primary_key=True

D default='[e-mail]'

unique=True ensures all values in the column are different.

What happens if you set nullable=False on a column?

A The column is ignored by the database

B The column can have empty values

C The column must always have a value

D The column automatically increments

nullable=False means the column cannot be empty or NULL.

Which of these is NOT a valid column type in Flask-SQLAlchemy?

A ArrayList

B String

C Integer

D Float

ArrayList is not a column type in Flask-SQLAlchemy.

Explain how to define a column with a type and constraints in Flask-SQLAlchemy.

Think about how you tell the database what kind of data to expect and rules for that data.

Why are constraints like unique and nullable important when designing database columns?

Consider how rules help keep your data clean and trustworthy.