Validation Types

Datachecks supports seven validation types. Each type covers a different aspect of data quality and exposes one or more functions you reference in the on field when configuring a validation.

Type	What it checks
Completeness	Missing values, nulls, and empty strings
Uniqueness	Duplicates and distinct counts
Validity	Formats, patterns, value ranges, and identifier standards
Reliability	Row counts, freshness, and timeliness
Numeric Distribution	Statistical measures across numeric columns
Custom SQL	Any metric expressible as a SQL query
Delta Validation	Differences between two data sources or segments

Completeness

Completeness validations detect missing data — null values and empty strings — in your datasets.

Function	Description
`count_null(column)`	Count of null values in the column.
`percent_null(column)`	Percentage of null values in the column.
`count_empty_string(column)`	Count of empty string (`''`) values in the column.
`percent_empty_string(column)`	Percentage of empty string values in the column.

Example

validations for product_db.products:
  - null_count_in_first_name:
      on: count_null(first_name)
      threshold: "= 0"

Uniqueness

Uniqueness validations measure data distinctiveness and identify duplication within a column.

Function	Description
`count_distinct(column)`	Count of unique values in the column.
`count_duplicate(column)`	Count of duplicate values in the column.

Example

validations for product_db.products:
  - distinct_count_of_product_categories:
      on: count_distinct(product_category)
      threshold: "> 5"

Validity

Validity validations check that values conform to expected formats, standards, or patterns.

Value-based

Function	Description
`count_valid_values(column)`	Count of values matching the `values` list.
`percent_valid_values(column)`	Percentage of values matching the `values` list.
`count_invalid_values(column)`	Count of values not in the `values` list.
`percent_invalid_values(column)`	Percentage of values not in the `values` list.

Use the values parameter to specify the accepted list:

validations for iris_db.iris:
  - valid_species_percentage:
      on: percent_valid_values(species)
      values: ["setosa", "virginica"]
      threshold: "> 65"

String format

Function	Description
`string_length_max(column)`	Maximum string length in the column.
`string_length_min(column)`	Minimum string length in the column.
`string_length_average(column)`	Average string length in the column.
`count_all_space(column)`	Count of values that are only whitespace.
`percent_all_space(column)`	Percentage of values that are only whitespace.
`count_null_keyword(column)`	Count of null-like string keywords (e.g. `"null"`, `"N/A"`).
`percent_null_keyword(column)`	Percentage of null-like string keywords.

Regex patterns

Function	Description
`count_valid_regex(column)`	Count of values matching the `pattern`.
`percent_valid_regex(column)`	Percentage of values matching the `pattern`.
`count_invalid_regex(column)`	Count of values not matching the `pattern`.
`percent_invalid_regex(column)`	Percentage of values not matching the `pattern`.

Use the pattern parameter to specify the regex:

validations for users_db.accounts:
  - valid_email_format:
      on: percent_valid_regex(email)
      pattern: "^[\\w.+-]+@[\\w-]+\\.[\\w.]+$"
      threshold: "> 99"

Contact information

Function	Description
`count_usa_phone(column)`	Count of valid US phone numbers.
`percent_usa_phone(column)`	Percentage of valid US phone numbers.
`count_email(column)`	Count of valid email addresses.
`percent_email(column)`	Percentage of valid email addresses.

Identifiers

Function	Description
`count_uuid(column)`	Count of valid UUIDs.
`percent_uuid(column)`	Percentage of valid UUIDs.
`count_sedol(column)`	Count of valid SEDOL codes.
`percent_sedol(column)`	Percentage of valid SEDOL codes.
`count_cusip(column)`	Count of valid CUSIP codes.
`percent_cusip(column)`	Percentage of valid CUSIP codes.
`count_lei(column)`	Count of valid LEI codes.
`percent_lei(column)`	Percentage of valid LEI codes.
`count_figi(column)`	Count of valid FIGI codes.
`percent_figi(column)`	Percentage of valid FIGI codes.
`count_isin(column)`	Count of valid ISIN codes.
`percent_isin(column)`	Percentage of valid ISIN codes.

Geolocation

Function	Description
`count_latitude(column)`	Count of valid latitude values (−90 to 90).
`percent_latitude(column)`	Percentage of valid latitude values.
`count_longitude(column)`	Count of valid longitude values (−180 to 180).
`percent_longitude(column)`	Percentage of valid longitude values.

Timestamps and dates

Function	Description
`count_timestamp_string(column)`	Count of values in valid ISO timestamp format.
`percent_timestamp_string(column)`	Percentage of values in valid ISO timestamp format.
`count_not_in_future(column)`	Count of timestamps that are not in the future.
`percent_not_in_future(column)`	Percentage of timestamps that are not in the future.
`count_date_not_in_future(column)`	Count of dates that are not in the future.
`percent_date_not_in_future(column)`	Percentage of dates that are not in the future.

Reliability

Reliability validations monitor data freshness, row counts, and update frequency to detect pipeline delays or data loss.

Function	Description
`freshness(timestamp_column)`	Time in seconds since the most recent value in the column. Alert when stale.
`count_rows`	Total row count in the table.
`count_documents`	Total document count in a search index.

Examples

validations for product_db.products:
  - freshness_of_products:
      on: freshness(updated_at)
      threshold: "> 86400"

  - product_row_count:
      on: count_rows
      where: "country_code = 'IN'"
      threshold: "> 1000"

Numeric Distribution

Numeric Distribution validations track statistical measures on numeric columns to detect shifts, outliers, or unexpected variance.

Central tendency

Function	Description
`avg(column)`	Mean value.
`min(column)`	Minimum value.
`max(column)`	Maximum value.
`sum(column)`	Sum of all values.

Dispersion

Function	Description
`variance(column)`	Variance from the mean.
`stddev(column)`	Standard deviation.

Percentiles

Function	Description
`percentile(column, 20)`	20th percentile value.
`percentile(column, 40)`	40th percentile value.
`percentile(column, 60)`	60th percentile value.
`percentile(column, 80)`	80th percentile value.
`percentile(column, 90)`	90th percentile value.

Zero and negative values

Function	Description
`count_zero(column)`	Count of zero values.
`percent_zero(column)`	Percentage of zero values.
`count_negative(column)`	Count of negative values.
`percent_negative(column)`	Percentage of negative values.

Example

validations for sales_db.orders:
  - average_order_value:
      on: avg(order_total)
      threshold: "< 500"

  - negative_amounts:
      on: count_negative(order_total)
      threshold: "= 0"

Custom SQL

Custom SQL validations let you define any metric as a SQL SELECT statement that returns a single numeric value. Use this for business-specific checks that don’t fit standard types. Configuration

Parameter	Description
`on`	Must be set to `custom_sql`.
`query`	The SQL query. Must return a single numeric value.

Example

validations for mysql_db.student:
  - high_age_bangalore_students:
      on: custom_sql
      query: |
        SELECT COUNT(*) FROM student
        WHERE city = 'bangalore' AND age >= 30
      threshold: "> 0"

Supported on all connected databases: Snowflake, BigQuery, Databricks, PostgreSQL, MySQL, Oracle, Azure SQL, and Sybase.

Delta Validation

Delta validations compare a metric between two datasets — useful for migration checks, cross-environment comparisons, and change detection. Configuration

Parameter	Description
`on`	`delta` followed by a supported function, e.g. `delta count_rows`.
`ref`	Reference asset in the format `datasource_name.dataset_name`.
`threshold`	The acceptable difference between the two values.

Supported functions

Function	Description
`delta count_rows`	Compare row counts between source and reference.

Example

validations for iris_pgsql_source.dcs_iris:
  - row_count_delta:
      on: delta count_rows
      ref: iris_pgsql_target.dcs_iris
      threshold: "< 1"

Getting Started

Agents

Integrations

Features

Reference

Completeness

Uniqueness

Validity

Value-based

String format

Regex patterns

Contact information

Identifiers

Geolocation

Timestamps and dates

Reliability

Numeric Distribution

Central tendency

Dispersion

Percentiles

Zero and negative values

Custom SQL

Delta Validation

Getting Started

Agents

Integrations

Features

Reference

​Completeness

​Uniqueness

​Validity

​Value-based

​String format

​Regex patterns

​Contact information

​Identifiers

​Geolocation

​Timestamps and dates

​Reliability

​Numeric Distribution

​Central tendency

​Dispersion

​Percentiles

​Zero and negative values

​Custom SQL

​Delta Validation

Completeness

Uniqueness

Validity

Value-based

String format

Regex patterns

Contact information

Identifiers

Geolocation

Timestamps and dates

Reliability

Numeric Distribution

Central tendency

Dispersion

Percentiles

Zero and negative values

Custom SQL

Delta Validation