Measures
Measures are aggregations performed on columns in your model. They can be used as final metrics or as building blocks for more complex metrics.
Measures have several inputs, which are described in the following table along with their field types.
| Parameter | Description | Required | Type |
|---|---|---|---|
name | Provide a name for the measure, which must be unique and can't be repeated across all semantic models in your dbt project. | Required | String |
description | Describes the calculated measure. | Optional | String |
agg | dbt supports the following aggregations: sum, max, min, average, median, count_distinct, percentile, and sum_boolean. | Required | String |
expr | Either reference an existing column in the table or use a SQL expression to create or derive a new one. | Optional | String |
non_additive_dimension | Non-additive dimensions can be specified for measures that cannot be aggregated over certain dimensions, such as bank account balances, to avoid producing incorrect results. | Optional | String |
agg_params | Specific aggregation properties, such as a percentile. | Optional | Dict |
agg_time_dimension | The time field. Defaults to the default agg time dimension for the semantic model. | Optional | String |
label | String that defines the display value in downstream tools. Accepts plain text, spaces, and quotes (such as orders_total or "orders_total"). Available in dbt version 1.7 or higher. | Optional | String |
create_metric | Create a simple metric from a measure by setting create_metric: True. The label and description attributes will be automatically propagated to the created metric. Available in dbt version 1.7 or higher. | Optional | Boolean |
Measure spec
An example of the complete YAML measures spec is below. The actual configuration of your measures will depend on the aggregation you're using.
measures:
- name: The name of the measure
description: 'same as always' ## Optional
agg: the aggregation type.
expr: the field
agg_params: 'specific aggregation properties such as a percentile' ## Optional
agg_time_dimension: The time field. Defaults to the default agg time dimension for the semantic model. ## Optional
non_additive_dimension: 'Use these configs when you need non-additive dimensions.' ## Optional
Name
When you create a measure, you can either give it a custom name or use the name of the data platform column directly. If the measure's name differs from the column name, you need to add an expr to specify the column name. The name of the measure is used when creating a metric.
Measure names must be unique across all semantic models in a project and can not be the same as an existing entity or dimension within that same model.
Description
The description describes the calculated measure. It's strongly recommended you create verbose and human-readable descriptions in this field.
Aggregation
The aggregation determines how the field will be aggregated. For example, a sum aggregation type over a granularity of day would sum the values across a given day.
Supported aggregations include:
| Aggregation types | Description |
|---|---|
| sum | Sum across the values |
| min | Minimum across the values |
| max | Maximum across the values |
| average | Average across the values |
| sum_boolean | A sum for a boolean type |
| count_distinct | Distinct count of values |
| median | Median (p50) calculation across the values |
| percentile | Percentile calculation across the values. |
Percentile aggregation example
If you're using the percentile aggregation, you must use the agg_params field to specify details for the percentile aggregation (such as what percentile to calculate and whether to use discrete or continuous calculations).
name: p99_transaction_value
description: The 99th percentile transaction value
expr: transaction_amount_usd
agg: percentile
agg_params:
percentile: .99
use_discrete_percentile: False # False calculates the continuous percentile, True calculates the discrete percentile.
Percentile across supported engine types
The following table lists which SQL engine supports continuous, discrete, approximate, continuous, and approximate discrete percentiles.
| Cont. | Disc. | Approx. cont | Approx. disc | |
|---|---|---|---|---|
| Snowflake | Yes | Yes | Yes (t-digest) | No |
| Bigquery | No (window) | No (window) | Yes | No |
| Databricks | Yes | No | No | Yes |
| Redshift | Yes | No (window) | No | Yes |
| Postgres | Yes | Yes | No | No |
| DuckDB | Yes | Yes | Yes (t-digest) | No |
Expr
If the name you specified for a measure doesn't match a column name in your model, you can use the expr parameter instead. This allows you to use any valid SQL to manipulate an underlying column name into a specific output. The name parameter then serves as an alias for your measure.
Notes: When using SQL functions in the expr parameter, always use data platform-specific SQL. This is because outputs may differ depending on your specific data platform.
For Snowflake users, if you use a week-level function in the expr parameter, it'll now return Monday as the default week start day based on ISO standards. If you have any account or session level overrides for the WEEK_START parameter that fixes it to a value other than 0 or 1, you will still see Monday as the week starts.
If you use the dayofweek function in the expr parameter with the legacy Snowflake default of WEEK_START = 0, it will now return ISO-standard values of 1 (Monday) through 7 (Sunday) instead of Snowflake's legacy default values of 0 (Monday) through 6 (Sunday).
Model with different aggregations
semantic_models:
- name: transactions
description: A record of every transaction that takes place. Carts are considered multiple transactions for each SKU.
model: ref('schema.transactions')
defaults:
agg_time_dimension: transaction_date
# --- entities ---
entities:
- name: transaction_id
type: primary
- name: customer_id
type: foreign
- name: store_id
type: foreign
- name: product_id
type: foreign
# --- measures ---
measures:
- name: transaction_amount_usd
description: Total USD value of transactions
expr: transaction_amount_usd
agg: sum
- name: transaction_amount_usd_avg
description: Average USD value of transactions
expr: transaction_amount_usd
agg: average
- name: transaction_amount_usd_max
description: Maximum USD value of transactions
expr: transaction_amount_usd
agg: max
- name: transaction_amount_usd_min
description: Minimum USD value of transactions
expr: transaction_amount_usd
agg: min
- name: quick_buy_transactions
description: The total transactions bought as quick buy
expr: quick_buy_flag
agg: sum_boolean
- name: distinct_transactions_count
description: Distinct count of transactions
expr: transaction_id
agg: count_distinct
- name: transaction_amount_avg
description: The average value of transactions
expr: transaction_amount_usd
agg: average
- name: transactions_amount_usd_valid # Notice here how we use expr to compute the aggregation based on a condition
description: The total USD value of valid transactions only
expr: CASE WHEN is_valid = True then transaction_amount_usd else 0 end
agg: sum
- name: transactions
description: The average value of transactions.
expr: transaction_amount_usd
agg: average
- name: p99_transaction_value
description: The 99th percentile transaction value
expr: transaction_amount_usd
agg: percentile
agg_params:
percentile: .99
use_discrete_percentile: False # False calculates the continuous percentile, True calculates the discrete percentile.
- name: median_transaction_value
description: The median transaction value
expr: transaction_amount_usd
agg: median
# --- dimensions ---
dimensions:
- name: transaction_date
type: time
expr: date_trunc('day', ts) # expr refers to underlying column ts
type_params:
time_granularity: day
- name: is_bulk_transaction
type: categorical
expr: case when quantity > 10 then true else false end
Non-additive dimensions
Some measures cannot be aggregated over certain dimensions, like time, because it could result in incorrect outcomes. Examples include bank account balances where it does not make sense to carry over balances month-to-month, and monthly recurring revenue where daily recurring revenue cannot be summed up to achieve monthly recurring revenue. You can specify non-additive dimensions to handle this, where certain dimensions are excluded from aggregation.
To demonstrate the configuration for non-additive measures, consider a subscription table that includes one row per date of the registered user, the user's active subscription plan(s), and the plan's subscription value (revenue) with the following columns:
date_transaction: The daily date-spine.user_id: The ID of the registered user.subscription_plan: A column to indicate the subscription plan ID.subscription_value: A column to indicate the monthly subscription value (revenue) of a particular subscription plan ID.
Parameters under the non_additive_dimension will specify dimensions that the measure should not be aggregated over.
| Parameter | Description | Field type |
|---|---|---|
name | This will be the name of the time dimension (that has already been defined in the data source) that the measure should not be aggregated over. | Required |
window_choice | Choose either min or max, where min reflects the beginning of the time period and max reflects the end of the time period. | Required |
window_groupings | Provide the entities that you would like to group by. | Optional |
semantic_models:
- name: subscriptions
description: A subscription table with one row per date for each active user and their subscription plans.
model: ref('your_schema.subscription_table')
defaults:
agg_time_dimension: subscription_date
entities:
- name: user_id
type: foreign
primary_entity: subscription
dimensions:
- name: subscription_date
type: time
expr: date_transaction
type_params:
time_granularity: day
measures:
- name: count_users
description: Count of users at the end of the month
expr: user_id
agg: count_distinct
non_additive_dimension:
name: subscription_date
window_choice: max
- name: mrr
description: Aggregate by summing all users' active subscription plans
expr: subscription_value
agg: sum
non_additive_dimension:
name: subscription_date
window_choice: max
- name: user_mrr
description: Group by user_id to achieve each user's MRR
expr: subscription_value
agg: sum
non_additive_dimension:
name: subscription_date
window_choice: max
window_groupings:
- user_id
metrics:
- name: mrr_metrics
type: simple
type_params:
measure: mrr
We can query the semi-additive metrics using the following syntax:
For dbt Cloud:
dbt sl query --metrics mrr_by_end_of_month --group-by subscription__subscription_date__month --order subscription__subscription_date__month
dbt sl query --metrics mrr_by_end_of_month --group-by subscription__subscription_date__week --order subscription__subscription_date__week
For dbt Core:
mf query --metrics mrr_by_end_of_month --group-by subscription__subscription_date__month --order subscription__subscription_date__month
mf query --metrics mrr_by_end_of_month --group-by subscription__subscription_date__week --order subscription__subscription_date__week
Dependencies
Metric nodes will reflect dependencies on semantic models based on their measures. However, dependencies based on filters should not be reflected in:
- dbt selection syntax
- Visualization of the DAG in dbt-docs and the integrated development environment (IDE).
This is because metrics need to source nodes for their depends_on attribute from a few different places:
RATIOandDERIVEDtype metrics should referenceMetric.type_params.input_metrics.SIMPLEtype metrics should referenceMetric.type_params.measure.
For example, when you run the command dbt list --select my_semantic_model+, it will show you the metrics that belong to the specified semantic model.
But there's a condition: Only the metrics that actually use measures or derived metrics from that semantic model will be included in the list. In other words, if a metric only uses a dimension from the semantic model in its filters, it won't be considered as part of that semantic model.