Merge Node Examples: Data Aggregation & Joins

Merge Node Examples: Data Aggregation & Joins

High-Level Summary

This workflow is an interactive tutorial that demonstrates the most common and powerful operations of n8n's Merge node. It shows how to combine data from two different sources using operations similar to SQL joins (Inner Join, Left Join, and Union All). Using simple, relatable examples like recipe ingredients and rock band members, this workflow visually explains how to filter, enrich, and merge datasets. It is designed as a learning tool for users who want to understand data aggregation patterns in n8n without needing external services or credentials.

Step-by-Step Node Breakdown

1. On clicking 'execute' (Manual Trigger) — No auth

• Type: n8n-nodes-base.manualTrigger
• Parameters: None (no configuration needed)
• Purpose: Starts the workflow when the user clicks the "Execute Workflow" button in the n8n editor. This is a manual trigger, ideal for testing and learning.

2. A. Ingredients Needed (Code) — No auth

• Type: n8n-nodes-base.code
• Parameters: Returns a static array of 5 ingredient objects: Flour, Eggs, Milk, Lemon, Sugar.
• Purpose: Simulates a list of ingredients required for a recipe (Dataset A).

3. B. Ingredients in stock (Code) — No auth

• Type: n8n-nodes-base.code
• Parameters: Returns a static array of 3 ingredient objects: Eggs, Lemon, Sugar.
• Purpose: Simulates a list of ingredients currently available in stock (Dataset B).

4. Ingredients in stock from recipe (Merge) — No auth

• Type: n8n-nodes-base.merge
• Parameters:
  • mode: combine (Merge mode)
  • mergeByFields: Matches on Name field from both inputs
  • options: None (default behavior)
• Purpose: Performs an Inner Join — keeps only ingredients from Dataset A (Ingredients Needed) that also exist in Dataset B (Ingredients in stock). Output: Eggs, Lemon, Sugar.

5. A. Ingredients (Code) — No auth

• Type: n8n-nodes-base.code
• Parameters: Returns the same static array as node 2 (5 ingredients).
• Purpose: Provides Dataset A for the enrichment example.

6. B. Recipe quantities (Code) — No auth

• Type: n8n-nodes-base.code
• Parameters: Returns a static array of 5 ingredient objects with Name and Quantity fields (e.g., Flour: 100g, Eggs: 2, Salt: 50g, Lemon: 1, Sugar: 6tbsp).
• Purpose: Simulates a dataset with additional quantity information (Dataset B).

7. Merge recipe (Merge) — No auth

• Type: n8n-nodes-base.merge
• Parameters:
  • mode: combine
  • joinMode: enrichInput1 (Left Join)
  • mergeByFields: Matches on Name field from both inputs
• Purpose: Performs a Left Join — keeps all items from Dataset A (Ingredients) and enriches them with matching data from Dataset B (Recipe quantities). For example, Flour gets Quantity: 100g, while Milk (no match in B) gets no quantity.

8. A. Queen (Code) — No auth

• Type: n8n-nodes-base.code
• Parameters: Returns a static array of 4 objects representing Queen band members (e.g., Freddy Mercury, Brian May).
• Purpose: Provides Dataset A for the Union All example.

9. B. Led Zeppelin (Code) — No auth

• Type: n8n-nodes-base.code
• Parameters: Returns a static array of 4 objects representing Led Zeppelin band members (e.g., Jimmy Page, Robert Plant).
• Purpose: Provides Dataset B for the Union All example.

10. Super Band (Merge) — No auth

• Type: n8n-nodes-base.merge
• Parameters:
  • mode: combine (default, no join mode specified)
  • No merge fields configured
• Purpose: Performs a Union All — combines all items from both datasets into a single list. The result is a "super band" with 8 members (Queen + Led Zeppelin). Unlike SQL Union All, this does not require identical field structures.

11. Note / Note1 / Note2 / Note4 / Note6 / Note8 / Note9 (Sticky Notes) — No auth

• Type: n8n-nodes-base.stickyNote
• Parameters: Each contains explanatory text describing the purpose of adjacent merge operations.
• Purpose: Provide inline documentation and visual guidance within the workflow canvas.

Setup Instructions

This workflow requires no external services, accounts, or credentials. It is entirely self-contained using static data generated by Code nodes. To use it:

1. Import the workflow into your n8n instance (version 0.200.0 or later recommended).
2. Click the "Execute Workflow" button to run all branches simultaneously.
3. Double-click on any Merge node to inspect its input and output data.
4. Read the sticky notes for explanations of each merge operation.

No API keys, database connections, or third-party accounts are needed.

Use Cases and Variations

This workflow is primarily an educational template for understanding data merging patterns. You can adapt it to real-world scenarios:

• Inner Join (Ingredients in stock): Use when you need to filter records that exist in both datasets — e.g., matching customer emails from two lists, or finding products that are both in a catalog and in stock.
• Left Join / Enrichment (Merge recipe): Use when you have a primary dataset and want to add supplementary information from another source — e.g., enriching user profiles with purchase history, or adding product prices to an order list.
• Union All (Super Band): Use when you need to combine two or more datasets with different structures into a single list — e.g., merging leads from multiple marketing channels, or consolidating reports from different departments.

To adapt this workflow:

• Replace Code nodes with real data sources (HTTP Request, Database, Google Sheets, etc.)
• Change merge fields to match your actual data schema
• Add output nodes (e.g., Send Email, Write to Database, Create File) to act on the merged results
• Schedule the workflow using a Cron or Schedule trigger for recurring data processing tasks

{
  "meta": {
    "instanceId": "8c8c5237b8e37b006a7adce87f4369350c58e41f3ca9de16196d3197f69eabcd"
  },
  "nodes": [
    {
      "id": "9971f7ab-ecc3-468b-8eb9-b58491b660bd",
      "name": "On clicking 'execute'",
      "type": "n8n-nodes-base.manualTrigger",
      "position": [
        1040,
        360
      ],
      "parameters": {},
      "typeVersion": 1
    },
    {
      "id": "bb212963-9b6f-434c-9777-3360fb456d4b",
      "name": "Note",
      "type": "n8n-nodes-base.stickyNote",
      "position": [
        1320,
        600
      ],
      "parameters": {
        "width": 1020,
        "height": 360,
        "content": "# 3. Add items from B below items from A\n"
      },
      "typeVersion": 1
    },
    {
      "id": "cc9461f1-1016-4ef5-bc10-525942c45047",
      "name": "Note1",
      "type": "n8n-nodes-base.stickyNote",
      "position": [
        1320,
        -200
      ],
      "parameters": {
        "width": 1020,
        "height": 380,
        "content": "# 1. Keep items from A if there's a match in B\n"
      },
      "typeVersion": 1
    },
    {
      "id": "09a68f64-5b2d-43a8-acff-7c26817cc025",
      "name": "Note2",
      "type": "n8n-nodes-base.stickyNote",
// ... truncated (copy to see full JSON)