ref() function for model dependencies in dbt - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the ref() function in dbt?

The ref() function creates a dependency between dbt models by referencing one model inside another. It helps dbt understand the order to run models and manage dependencies automatically.

beginner

How does ref() help with model dependency management?

ref() tells dbt which models depend on others. This way, dbt runs models in the right order and rebuilds only what is needed when data or logic changes.

intermediate

What happens if you use ref('model_name') inside a model SQL file?

Using ref('model_name') inserts the correct table or view name for that model in the compiled SQL. It also creates a dependency link so dbt knows to build that model first.

intermediate

Can you use ref() to reference models across different dbt projects?

No, ref() only works within the same dbt project. To reference models across projects, you need to use other methods like external tables or sources.

beginner

Why is it better to use ref() instead of hardcoding table names in dbt models?

Using ref() makes your project more flexible and maintainable. If table names or schemas change, dbt updates references automatically. Hardcoding names can cause errors and extra work.

What does the ref() function do in dbt?

A Creates a dependency between models

B Runs SQL queries faster

C Deletes old models

D Generates documentation

ref() creates dependencies so dbt knows the order to build models.

Which of these is a benefit of using ref() in dbt?

A Automatically manages model build order

B Encrypts data in models

C Improves network speed

D Creates new database users

ref() helps dbt run models in the correct order based on dependencies.

What happens if you hardcode table names instead of using ref()?

A dbt ignores dependencies

B dbt runs models faster

C Models automatically update schema

D Your project becomes less flexible and error-prone

Hardcoding table names can cause errors if names or schemas change, unlike ref() which updates automatically.

Can ref() be used to reference models in other dbt projects?

A Yes, across any projects

B Only if projects share the same database

C No, only within the same project

D Only for models in the same folder

ref() works only within the same dbt project.

What does ref('model_name') return inside a model SQL file?

A The database connection string

B The compiled table or view name for that model

C The raw SQL code of the model

D The model's documentation URL

ref() inserts the correct compiled table or view name for the referenced model.

Explain how the ref() function helps dbt manage model dependencies and build order.

Think about how dbt knows which model to build first.

Describe why using ref() is better than hardcoding table names in dbt models.

Consider what happens if a table name changes in your project.

Practice

1. What is the main purpose of the ref() function in dbt?

easy

A. To create new database users

B. To write raw SQL queries inside dbt models

C. To link models and define dependencies between them

D. To schedule dbt runs automatically

Solution

1. Step 1: Understand the role of ref()

   The ref() function is used to link one model to another in dbt, so dbt knows the order to run models and their dependencies.

2. Step 2: Identify what ref() does not do

   It does not write raw SQL, create users, or schedule runs. Its main role is linking models.

3. Final Answer:

   To link models and define dependencies between them -> Option C

4. Quick Check:

   ref() links models = A [OK]

Hint: Remember: ref() connects models, not SQL or users [OK]

Common Mistakes:

• Thinking ref() writes SQL code
• Confusing ref() with scheduling tools
• Assuming ref() manages database users

2. Which of the following is the correct syntax to reference a model named customers inside another model using ref()?

easy

A. select * from {{ ref('customers') }}

B. select * from ref('customers')

C. select * from ref(customers)

D. select * from {{ ref(customers) }}

Solution

1. Step 1: Recall dbt Jinja syntax for ref()

   In dbt, ref() must be wrapped in double curly braces and the model name must be a string in quotes.

2. Step 2: Check each option

   select * from {{ ref('customers') }} uses {{ ref('customers') }} which is correct. Options B and C miss the curly braces or quotes. select * from {{ ref(customers) }} misses quotes around the model name.

3. Final Answer:

   select * from {{ ref('customers') }} -> Option A

4. Quick Check:

   Use {{ ref('model_name') }} syntax = A [OK]

Hint: Always use {{ ref('model_name') }} with quotes and braces [OK]

Common Mistakes:

• Omitting curly braces {{ }}
• Not putting model name in quotes
• Using ref() without Jinja syntax

3. Given the following dbt model code, what will be the output SQL after compilation if the orders model exists?

select order_id, customer_id
from {{ ref('orders') }}

medium

A. select order_id, customer_id from orders

B. select order_id, customer_id from {{ ref('orders') }}

C. select order_id, customer_id from dbt.orders

D. select order_id, customer_id from ref('orders')

Solution

1. Step 1: Understand what ref() compiles to

   The ref() function compiles to the actual table name of the referenced model, usually just the model name like 'orders'.

2. Step 2: Check the compiled SQL output

   The compiled SQL replaces {{ ref('orders') }} with orders, so the output is select order_id, customer_id from orders.

3. Final Answer:

   select order_id, customer_id from orders -> Option A

4. Quick Check:

   ref('orders') compiles to orders = C [OK]

Hint: ref() compiles to the model's table name without braces [OK]

Common Mistakes:

• Leaving ref() uncompiled in SQL
• Adding extra schema prefix without config
• Using ref() as a string literal

4. You wrote this dbt model code:

select * from ref('sales')

When you run dbt, you get an error. What is the problem?

medium

A. Quotes around 'sales' should be removed

B. Model name 'sales' does not exist

C. ref() cannot be used inside select statements

D. Missing double curly braces around ref()

Solution

1. Step 1: Check the syntax of ref() usage

   In dbt, ref() must be wrapped in double curly braces to be interpreted as Jinja code.

2. Step 2: Identify the error cause

   The code uses ref('sales') without {{ }}, so dbt treats it as plain text, causing an error.

3. Final Answer:

   Missing double curly braces around ref() -> Option D

4. Quick Check:

   Use {{ ref('model') }} not ref('model') alone = D [OK]

Hint: Always wrap ref() in {{ }} to avoid errors [OK]

Common Mistakes:

• Forgetting {{ }} around ref()
• Assuming ref() works without Jinja
• Removing quotes from model name

5. You have two models: customers and orders. You want to create a new model customer_orders that joins these two. Which is the best way to use ref() to ensure correct dependencies and flexible naming?

hard

A. select c.customer_id, o.order_id from customers c join orders o on c.customer_id = o.customer_id

B. select c.customer_id, o.order_id from {{ ref('customers') }} c join {{ ref('orders') }} o on c.customer_id = o.customer_id

C. select c.customer_id, o.order_id from 'customers' c join 'orders' o on c.customer_id = o.customer_id

D. select c.customer_id, o.order_id from ref('customers') c join ref('orders') o on c.customer_id = o.customer_id

Solution

1. Step 1: Use ref() with correct Jinja syntax for both models

   To link models and ensure dbt knows dependencies, use {{ ref('model_name') }} for both customers and orders.

2. Step 2: Avoid hardcoding table names or missing Jinja syntax

   Options A and C hardcode names or use quotes incorrectly. select c.customer_id, o.order_id from ref('customers') c join ref('orders') o on c.customer_id = o.customer_id misses curly braces, so it won't compile.

3. Final Answer:

   select c.customer_id, o.order_id from {{ ref('customers') }} c join {{ ref('orders') }} o on c.customer_id = o.customer_id -> Option B

4. Quick Check:

   Use {{ ref('model') }} for all dependencies = B [OK]

Hint: Use {{ ref('model') }} for all model references [OK]

Common Mistakes:

• Hardcoding table names instead of using ref()
• Forgetting curly braces around ref()
• Using quotes incorrectly around model names