Querying with filter and filter_by in Flask - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the difference between filter() and filter_by() in Flask SQLAlchemy?

filter() accepts SQL expressions and allows complex queries using operators, while filter_by() uses keyword arguments for simple equality checks.

beginner

How do you write a query to find all users with the name 'Alice' using filter_by()?

Use User.query.filter_by(name='Alice').all() to get all users named Alice.

beginner

Write a query using filter() to find users older than 30.

Use User.query.filter(User.age > 30).all() to get users older than 30.

intermediate

Can filter_by() handle complex conditions like age > 30?

No, filter_by() only supports simple equality checks. Use filter() for complex conditions.

beginner

What does .all() do at the end of a query?

.all() runs the query and returns a list of all matching records.

Which method allows you to write complex SQL expressions in Flask queries?

A filter()

B filter_by()

C all()

D get()

filter() accepts SQL expressions for complex queries, unlike filter_by() which uses simple keyword arguments.

How would you find all users with the email '[e-mail]' using filter_by()?

A User.query.filter(email='[e-mail]').all()

B User.query.get(email='[e-mail]')

C User.query.filter_by(email='[e-mail]').all()

D User.query.all(email='[e-mail]')

filter_by() uses keyword arguments for simple equality filters.

What will User.query.filter(User.age > 25).all() return?

A Users younger than 25

B Users exactly 25 years old

C All users

D Users older than 25

The query filters users where age is greater than 25.

Which method is NOT suitable for filtering by multiple conditions like name='Bob' and age > 20?

A filter_by()

B filter(User.name=='Bob', User.age>20)

C filter().filter()

D filter()

filter_by() only supports simple equality and cannot handle multiple or complex conditions.

What does the all() method do after a query?

A Deletes all matching records

B Returns all matching records as a list

C Returns the first matching record

D Counts all matching records

all() executes the query and returns a list of all results.

Explain how to use filter() and filter_by() in Flask SQLAlchemy queries. When would you choose one over the other?

Think about the complexity of the condition you want to apply.

Describe how to find all users older than 30 using Flask SQLAlchemy. Include which method you use and why.

Remember which method supports operators like >.