Dbt Transformation Patterns

• sql
• analytics
• transformations

dbt Transformation Patterns

Overview

The dbt Transformation Patterns skill focuses on building production-grade analytics transformations with dbt—from project structure through testing and documentation. This is a specialized, deep-focus skill for analytics engineers and data engineers implementing SQL transformations.

Use this skill when:

• Building or restructuring a dbt project
• Implementing incremental models for large datasets
• Setting up testing and documentation
• Optimizing dbt model organization and materialization
• Creating reusable macros and transformations

Core Capabilities

• Project Architecture: Organize models into staging, intermediate, and marts layers
• Incremental Strategies: Choose delete+insert, merge, or insert-overwrite based on warehouse and data patterns
• Testing Framework: Design comprehensive test suites (schema, data quality, relationships)
• Documentation: Generate and maintain dbt docs, column-level lineage, model descriptions
• Macro Development: Build DRY, reusable SQL macros for common transformations
• Performance Tuning: Optimize dbt DAG, materialization strategy, and warehouse execution

When to Use

When to Use

• Building a new dbt project or restructuring an existing one
• Implementing incremental models for large fact/event tables
• Setting up automated testing and data quality validation
• Optimizing dbt performance (compile time, execution time, DAG structure)
• Creating reusable macros for transformations
• Establishing documentation and lineage standards

Workflow / Process

Phase 1: Project Structure

1. Define source system definitions and mappings
2. Design layer strategy (staging → intermediate → marts)
3. Establish naming conventions and materialization strategy

Phase 2: Model Development

1. Build staging models (1:1 with sources, light cleaning)
2. Create intermediate models (business logic, joins)
3. Build mart models (final dimension and fact tables)

Phase 3: Testing & Documentation

1. Add column and model tests
2. Define data quality expectations
3. Generate and validate dbt docs

Phase 4: Optimization

1. Tune materialization (view vs table vs ephemeral vs incremental)
2. Optimize incremental strategies for full-refresh vs run speed
3. Monitor dbt run time and warehouse costs

Standards & Best Practices

Project Organization

• Staging: 1:1 with sources, minimal transformations, documented column lineage
• Intermediate: Business logic, joins, aggregations; ephemeral unless reused
• Marts: Final analytics tables (dimensions and facts), fully tested
• Naming: stg_ (staging), int_ (intermediate), dim_/fct_ (marts)

Testing Strategy

• Schema Tests: Column-level (not null, unique) on all key columns
• Relationship Tests: Foreign key integrity to upstream models
• Custom Tests: Business rule validation (amounts >= 0, statuses in enum)
• Test Coverage: Goal is 100% on dimensions and facts; 80%+ on staging

Incremental Models

• Use for: Tables > 1M rows where full refresh becomes expensive
• Delete+Insert: Default; good for append-only data
• Merge: Best for tables with updates to existing rows
• Insert Overwrite: Partition-based; efficient for time-series data

Common Pitfalls

• Raw → Mart in One Model: Creates tech debt. Always stage data first.
• Hardcoded Dates: Use {{ var() }} for parameters, not hardcoded filters.
• Duplicate Logic: Extract repeated SQL to macros, not copy-paste.
• No Testing: Prevents bugs from propagating downstream. Test aggressively.
• Ignoring Source Freshness: Data staleness breaks analytics. Monitor it.
• Over-Materialization: Materialize as table only when necessary (marts, heavy joins).
• Not Using Incremental: Full refresh becomes expensive; incremental catches late arrivals.

Constraints

Technical Constraints:

• Cannot modify source system definitions without architect approval
• All models must pass testing before deployment
• Incremental strategies must handle late-arriving and updated data correctly

Scope Constraints:

• In Scope: Model development, SQL transformations, dbt macros, testing, documentation
• Out of Scope: Data pipeline orchestration (use data-pipeline-engineer), source system setup (use architect)

Integration Points

Reference Examples

See examples/ directory for:

• Complete project structure (staging/intermediate/marts)
• Source definitions and freshness monitoring
• Incremental model implementations
• Testing suites (schema, relationships, custom)
• Macro examples (DRY transformations)
• dbt commands reference

Version History:

• 1.0 (2026-01-24): dbt-focused analytics engineering skill

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