Built-in Jinja context variables in dbt - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of Jinja variable usage in dbt model

What is the output of this Jinja snippet in a dbt model if the model name is sales_summary?

dbt

{% set model_name = this.name %}
{{ model_name }}

A None

B this.name

C {{ this.name }}

D sales_summary

💡 Hint

The this variable refers to the current model's context.

The this.name returns the name of the current model as a string, so the output is 'sales_summary'.

❓ data_output

intermediate

Using var to pass variables in dbt

Given the dbt model code below, what will be the output of {{ var('region', 'all') }} if no variable region is passed during runtime?

dbt

{{ var('region', 'all') }}

A all

B region

C None

D Error: variable not found

💡 Hint

The var function returns the default value if the variable is not set.

Since no variable named 'region' is passed, the default value 'all' is returned.

🧠 Conceptual

advanced

Purpose of config in dbt Jinja context

Which of the following best describes the purpose of the config variable in dbt's Jinja context?

A It contains the database connection credentials.

B It stores the runtime environment variables for the dbt project.

C It allows setting model-specific configurations like materialization and tags.

D It holds the compiled SQL code of the model.

💡 Hint

Think about how you customize model behavior in dbt.

The config variable is used to set configurations such as materialization type, file paths, and tags for the current model.

🔧 Debug

advanced

Error caused by misuse of this in dbt model

What error will occur if you try to access this.database in a dbt model when the database is not defined in the profile?

dbt

{{ this.database }}

A None (outputs empty string)

B UndefinedError: 'database' is not defined on 'this'

C RuntimeError: Database connection failed

D KeyError: 'database'

💡 Hint

Check what happens when a property is missing in Jinja context.

If the database is not set, accessing this.database raises an UndefinedError because the attribute does not exist.

🚀 Application

expert

Using run_started_at for incremental models

You want to filter rows in an incremental dbt model to only include data updated after the current run started. Which Jinja variable should you use in your SQL WHERE clause?

A run_started_at

B this.schema

C target.name

D invocation_id

💡 Hint

This variable holds the timestamp when the dbt run began.

The run_started_at variable contains the timestamp of when the dbt run started, useful for filtering incremental data.

Practice

1. What does the built-in Jinja context variable run_started_at provide in dbt?

easy

A. The total number of models in the project

B. The name of the current model being executed

C. The timestamp when the current dbt run started

D. The database connection string

Solution

1. Step 1: Understand the purpose of run_started_at

   This variable holds the timestamp marking the start of the dbt run.

2. Step 2: Compare with other options

   Other options describe unrelated information like model name or connection details.

3. Final Answer:

   The timestamp when the current dbt run started -> Option C

4. Quick Check:

   run_started_at = Timestamp [OK]

Hint: Remember: run_started_at = run start time [OK]

Common Mistakes:

• Confusing run_started_at with model name
• Thinking it gives database info
• Assuming it counts models

2. Which of the following is the correct syntax to access the current model name using a built-in Jinja context variable in dbt?

easy

A. {{ this.name }}

B. {{ model_name }}

C. {{ this.model }}

D. {{ current_model }}

Solution

1. Step 1: Recall the correct variable for current model

   The variable this refers to the current model, and this.name gives its name.

2. Step 2: Check syntax correctness

   Only {{ this.name }} correctly accesses the model name in Jinja syntax.

3. Final Answer:

   {{ this.name }} -> Option A

4. Quick Check:

   Current model name = {{ this.name }} [OK]

Hint: Use this.name for current model name [OK]

Common Mistakes:

• Using undefined variables like model_name
• Missing dot notation after this
• Using incorrect variable names

3. Given the following dbt Jinja code snippet, what will be the output of {{ invocation_id }}?

{% set id = invocation_id %}{{ id }}

medium

A. The number of models executed so far

B. A unique identifier string for the current dbt run

C. The current timestamp

D. An error because invocation_id is undefined

Solution

1. Step 1: Understand what invocation_id represents

   This variable holds a unique string ID for the current dbt run invocation.

2. Step 2: Analyze the code snippet

   The code sets id to invocation_id and then outputs it, so it prints the unique run ID.

3. Final Answer:

   A unique identifier string for the current dbt run -> Option B

4. Quick Check:

   invocation_id = Unique run ID [OK]

Hint: invocation_id = unique run ID string [OK]

Common Mistakes:

• Thinking it counts models
• Confusing with timestamps
• Assuming it causes an error

4. You wrote this dbt Jinja code but get an error:

{{ run_started_at.strftime('%Y-%m-%d') }}

. What is the likely cause?

medium

A. run_started_at is a string, not a datetime object, so strftime fails

B. Missing parentheses after run_started_at

C. strftime is not a valid method in Jinja

D. You must use single curly braces instead of double

Solution

1. Step 1: Check the type of run_started_at

   In dbt, run_started_at is a string timestamp, not a datetime object.

2. Step 2: Understand why strftime fails

   Since it's a string, calling strftime (a datetime method) causes an error.

3. Final Answer:

   run_started_at is a string, not a datetime object, so strftime fails -> Option A

4. Quick Check:

   String type blocks datetime methods [OK]

Hint: run_started_at is string; convert before datetime methods [OK]

Common Mistakes:

• Assuming run_started_at is datetime
• Using single braces for Jinja variables
• Thinking strftime is unsupported in Jinja

5. You want to create a dbt model that adds a column with the current run's unique ID and the run start date in 'YYYY-MM-DD' format. Which Jinja code snippet correctly uses built-in context variables to achieve this?

hard

A. {% set run_date = run_started_at.split('-')[0] %}
SELECT *, '{{ invocation_id }}' AS run_id, '{{ run_date }}' AS run_date FROM {{ this }}

B. {% set run_date = run_started_at.strftime('%Y-%m-%d') %}
SELECT *, '{{ invocation_id }}' AS run_id, '{{ run_date }}' AS run_date FROM {{ this }}

C. SELECT *, '{{ invocation_id }}' AS run_id, '{{ run_started_at }}' AS run_date FROM {{ this }}

D. {% set run_date = run_started_at[:10] %}
SELECT *, '{{ invocation_id }}' AS run_id, '{{ run_date }}' AS run_date FROM {{ this }}

Solution

1. Step 1: Extract date from run_started_at string

   Since run_started_at is a string like 'YYYY-MM-DDTHH:MM:SS', slicing the first 10 characters gets the date.

2. Step 2: Use invocation_id and run_date in SELECT

   The snippet correctly sets run_date and uses both variables in the SELECT statement.

3. Step 3: Check other options for errors

   {% set run_date = run_started_at.strftime('%Y-%m-%d') %} SELECT *, '{{ invocation_id }}' AS run_id, '{{ run_date }}' AS run_date FROM {{ this }} tries to use strftime on a string (error). SELECT *, '{{ invocation_id }}' AS run_id, '{{ run_started_at }}' AS run_date FROM {{ this }} uses full timestamp, not formatted date. {% set run_date = run_started_at.split('-')[0] %} SELECT *, '{{ invocation_id }}' AS run_id, '{{ run_date }}' AS run_date FROM {{ this }} extracts only year incorrectly.

4. Final Answer:

   Extracts date with run_started_at[:10] and uses invocation_id -> Option D

5. Quick Check:

   Slice string for date, use invocation_id [OK]

Hint: Slice run_started_at[:10] for date, use invocation_id [OK]

Common Mistakes:

• Using strftime on string variable
• Not formatting run_started_at to date
• Extracting only year instead of full date