How to Create a Basic Parameter in Looker Using a
Variable
Looker is a powerful business intelligence (BI) tool that
enables users to analyze data, build custom reports, and create interactive
dashboards. One of Looker's most versatile features is the ability to use
parameters and variables to make your data models more dynamic and
user-friendly. This blog post will guide you through creating a basic parameter
in Looker using a variable, offering practical steps and examples to help you
harness the full potential of this feature.
What is a Parameter
in Looker?
In Looker, a parameter is a user-defined variable that can
be used to customize queries and control the behavior of your reports and
dashboards. Parameters allow you to create dynamic content and interactive
features that adapt to user inputs. They can be used to adjust filters, control
the display of data, or switch between different metrics.
Parameters are essential for creating interactive
dashboards, custom filters, and advanced data models. They enable users to
input values that can influence the results of their queries and
visualizations, providing a more tailored data experience.
What is a Variable in
Looker?
In Looker, a variable is a placeholder for a value that can
be dynamically set or modified. Variables are used in conjunction with
parameters to make your data models more flexible. While parameters define user
inputs, variables store and manage these inputs to be used in calculations,
filters, or other parts of your LookML model.
Variables in Looker are used to reference parameter values
and can be included in LookML code to control various aspects of your data
model. Understanding how to work with both parameters and variables is crucial
for building interactive and responsive data models.
Creating a Basic Parameter in Looker
To create a basic parameter in Looker using a variable,
follow these steps:
Step 1: Define Your
Parameter
1. Open LookML
Project: Go to the Looker development environment and open the LookML
project where you want to add the parameter.
2. Create a
Parameter: Navigate to the LookML file where you want to define the
parameter. This is typically done in a view file or a model file. Use the
`parameter` keyword to create a new parameter. Here’s an example of how to
define a simple parameter:
```lookml
parameter:
my_parameter {
type: string
default_value:
"default"
allowed_value:
"Option 1"
allowed_value:
"Option 2"
allowed_value:
"Option 3"
}
```
In this example:
- `type: string`
specifies that the parameter will accept text values.
- `default_value`
sets a default value for the parameter.
- `allowed_value`
defines the options available for the parameter.
3. Save Your Changes:
Save the LookML file to apply the new parameter definition.
Step 2: Use the Parameter in a Variable
1. Define a Variable:
Create a variable that will store the value of your parameter. This variable
will be used in your LookML code to apply the parameter’s value in queries and
calculations. Add the variable to the same LookML file where you defined the
parameter.
```lookml
dimension:
selected_option {
type: string
sql: {%
parameter my_parameter %} ;;
}
```
In this example,
the variable `selected_option` references the value of the `my_parameter`
parameter. The `sql` statement uses the LookML templating syntax to insert the
parameter value into the SQL query.
2. Apply the Variable
in Measures or Dimensions: Use the variable in your measures or dimensions
to control their behavior based on the parameter value. For example:
```lookml
measure:
total_sales {
type: sum
sql: CASE WHEN
{% parameter my_parameter %} = 'Option 1' THEN ${sales_amount} ELSE 0 END ;;
}
```
In this example,
the `total_sales` measure uses a `CASE` statement to conditionally sum sales
based on the value of `my_parameter`.
Step 3: Test Your Parameter and Variable
1. Explore Your Data:
Go to the Explore section in Looker and select the view where you added the
parameter and variable. You should see the new parameter available as a filter
or control.
2. Interact with the
Parameter: Adjust the parameter value using the control in the Explore
interface. Verify that the variable and associated measures or dimensions
update according to the parameter's value.
3. Verify Results:
Check that your data is being filtered or calculated correctly based on the
parameter value. Make sure that all expected behavior and calculations align
with your requirements.
Example Use Cases for Parameters and Variables
Here are a few practical use cases for using parameters and
variables in Looker:
1. Dynamic Filters
Parameters can be used to create dynamic filters that allow
users to select different criteria. For example, you could use a parameter to
let users choose between different regions or time periods, and a variable to
apply this filter to your data.
2. Custom Calculations
Variables can store parameter values that control custom
calculations. For instance, you could use a parameter to select different
metrics (e.g., revenue vs. profit) and a variable to adjust the calculations
accordingly.
3. Interactive Dashboards
Parameters enable interactive features in dashboards. For
example, you could create a parameter to switch between different
visualizations or charts based on user input, making your dashboard more
engaging and informative.
Best Practices for Using Parameters and
Variables
1. Name Parameters
and Variables Clearly: Use descriptive names for parameters and variables
to make your LookML code more readable and maintainable.
2. Provide Default
Values: Always set default values for parameters to ensure that your
queries and calculations have a fallback value if the user does not specify
one.
3. Test Thoroughly:
Before deploying changes to production, thoroughly test your parameters and
variables to ensure they work as expected and produce accurate results.
4.
Document Your LookML:
Include comments and documentation in your LookML code to explain the
purpose and usage of parameters and variables. This will help other developers
and users understand how to interact with your data models.
5. Consider
Performance Implications: Be mindful of the performance impact when using
parameters and variables in complex queries. Test the performance of your
LookML models to ensure they run efficiently with different parameter values.
Conclusion
Creating and using parameters and variables in Looker
provides powerful ways to enhance the interactivity and flexibility of your
data models. By following the steps outlined in this guide, you can create
basic parameters, apply them using variables, and leverage their capabilities
to build dynamic and responsive reports and dashboards.
Whether you’re creating custom filters, dynamic
calculations, or interactive dashboards, parameters and variables are essential
tools for making your Looker projects more versatile and user-friendly.
Experiment with different use cases and best practices to maximize the
potential of Looker’s parameter and variable features.
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