How to declare the while loop and then to use that loop in different models, does it used in macro, kindly provide with an example

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1

How to declare the while loop and then to use that loop in different models, does it used in macro, kindly provide with an example?

2

In dbt, you can’t use traditional while loops like in procedural programming languages, but you can achieve similar iterative logic using macros and Jinja templating. Macros in dbt work like reusable functions and allow you to loop through items dynamically.

  1. define a macro in your macros/ directory, like
{% macro generate_loop_statements(n) %}
  {% set queries = [] %}
  {% for i in range(n) %}
    {% do queries.append("SELECT {{ i }} AS loop_iteration") %}
  {% endfor %}
  {{ return(queries | join(" UNION ALL ")) }}
{% endmacro %}

then use this macro inside a model:
{{ generate_loop_statements(5) }}

and this will generate
SELECT 0 AS loop_iteration
UNION ALL
SELECT 1 AS loop_iteration
UNION ALL
SELECT 2 AS loop_iteration
UNION ALL
SELECT 3 AS loop_iteration
UNION ALL
SELECT 4 AS loop_iteration

If you need to reference this logic across different models, you can call the macro inside each model where needed.

3

Hi , I need to create while loop if the condition is true then i need to execute some models otherwise if the condition is false, it will execute other models. Can you provide an example for lets say condition while (a=b) then some models
else some other models.

4

Hi,

you can’t use a traditional while loop like in procedural languages, but you can control execution flow using conditional logic in macros.

If you want to run certain models based on a condition (a = b), the best approach is to use Jinja logic with dbt run-operation or pre/post hooks, like this example:

{% macro conditional_model_execution(a, b) %}
    {% if a == b %}
        {{ return(["model_a", "model_b"]) }}
    {% else %}
        {{ return(["model_x", "model_y"]) }}
    {% endif %}
{% endmacro %}

Then, in your dbt_project.yml, you can reference this macro to dynamically determine which models to run.

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