feat: add stddev macro (DNA-18084 / DNA-21718)

README.md

@@ -31,6 +31,7 @@ This dbt package contains macros for SQL functions to run the dbt project on mul
   - [date_add](#date_add-source)
   - [date_from_timestamp](#date_from_timestamp-source)
   - [datediff](#datediff-source)
+  - [stddev](#stddev-source)
   - [string_agg](#string_agg-source)
   - [timestamp_from_date](#timestamp_from_date-source)
   - [timestamp_from_parts](#timestamp_from_parts-source)
@@ -111,6 +112,12 @@ This macro generates an id field that can be used as a column for the current mo
 Usage:
 `{{ pm_utils.id() }}`
 
+#### stddev ([source](macros/multiple_databases/stddev.sql))
+This macro computes the standard deviation of a set of values, `null` values are ignored in the calculation. This macro can only be used as an aggregate function. For SQL Server, at least one of the values provided should not be `null`.
+
+Usage: 
+`{{ pm_utils.stddev('[expression]') }}`
+
 #### string_agg ([source](macros/multiple_databases/string_agg.sql))
 This macro aggregates string fields separated by the given delimiter. If no delimiter is specified, strings are separated by a comma followed by a space. This macro can only be used as an aggregate function. For SQL Server, the maximum supported length is 2000. 
 

dbt_project.yml

@@ -1,5 +1,5 @@
 name: 'pm_utils'
-version: '1.1.2'
+version: '1.2.0'
 config-version: 2
 
 require-dbt-version: [">=1.0.0", "<2.0.0"]

integration_tests/models/schema.yml

@@ -90,3 +90,12 @@ models:
       - equal_value:
           actual: '`add_to_null_value`'
           expected: '`add_to_null_value_expected`'
+
+  - name: test_stddev
+    tests:
+    - equal_value:
+        actual: '`stddev_actual`'
+        expected: '`stddev_expected`'
+    - equal_value:
+        actual: '`stddev_with_null_values_actual`'
+        expected: '`stddev_with_null_values_expected`'

integration_tests/models/test_stddev.sql

@@ -0,0 +1,30 @@
+with Input_data as (
+	select val
+    from (values (1),(2),(3),(4)) as Input(val)
+),
+
+Input_data_with_null as (
+	select val
+    from (values (1),(2),(null),(4)) as Input(val)
+),
+
+stddev_input_data as (
+    select
+        round({{ pm_utils.stddev('val') }}, 3) as `stddev_input_data`
+    from Input_data
+),
+
+stddev_input_data_null as (
+    select
+        round({{ pm_utils.stddev('val') }}, 3) as `stddev_input_data_null`
+    from Input_data_with_null
+)
+
+select
+    {{ pm_utils.to_varchar('stddev_input_data.`stddev_input_data`') }} as `stddev_actual`,
+    '1.291' as `stddev_expected`,
+
+    {{ pm_utils.to_varchar('stddev_input_data_null.`stddev_input_data_null`') }} as `stddev_with_null_values_actual`,
+    '1.528' as `stddev_with_null_values_expected`
+from stddev_input_data
+cross join stddev_input_data_null

macros/multiple_databases/stddev.sql

@@ -0,0 +1,9 @@
+{% macro stddev(field, relation) %}
+
+{%- if target.type in ('databricks', 'snowflake') -%}
+    stddev({{ field }})
+{%- elif target.type == 'sqlserver' -%}
+    stdev({{ field }})
+{%- endif -%}
+
+{% endmacro %}