Dwh.dev documentation
  • What is Dwh.dev?
  • Features
    • Data catalog
      • PIPEs
      • Fancy SQL Highlight
    • Data Lineage
      • Object-level lineage
      • Column-level Lineage
      • In-query lineage
      • Navigation
      • JOIN and WHERE
      • Equals column lineage
      • Strong and Weak dependencies
      • Default and Virtual Columns
      • Implicit Types casting
      • Circle dependencies
      • Argument forwarding
    • TASKs
  • Integrations
    • Snowflake
      • Offline mode
      • Secured online mode
      • Snowflake Marketplace
    • DBT
    • ETL
    • BI
      • Looker
      • Other
    • API
  • Snowflake SQL Syntax and Behavior
    • Identifiers
    • Reusing column aliases
    • SELECT * ILIKE EXCLUDE REPLACE RENAME
    • Scalar functions name resolution special behavior
    • Functions overloading
    • CTE as an expression alias
    • ASOF Join
    • UDF named arguments
    • Objects auto renaming
    • Columns auto renaming
Powered by GitBook
On this page

Was this helpful?

  1. Features
  2. Data Lineage

Strong and Weak dependencies

PreviousEquals column lineageNextDefault and Virtual Columns

Last updated 8 months ago

Was this helpful?

In the , we discussed displaying columns used in JOIN and WHERE clauses. But we wanted to go further :)

Even if columns are data sources, it makes sense to divide them into 2 categories: columns that are direct data sources and columns that only influence them.

For example:

SELECT
  ROUND(a, b)
FROM t

Here, column A is a direct data source, while B is not. B influences the result, but A is the primary source.

Another example:

SELECT
  CASE
    WHEN A IS NULL
      THEN B
    ELSE C 
  END
FROM t

Here, the value from A doesn't appear in the result but affects it.

At , we divided such dependencies into classes: STRONG and WEAK. We annotated all core functions to determine which argument belongs to which class. We also analyze CASE WHEN and other cases. You can disable any of these classes in the settings panel:

Youtube
JOIN and WHERE section
Dwh.dev
Weak dependencies