Blending data sources in Tableau - Cell-by-Cell Formula Trace

Sample Data

Two data sources: Sales data with Order ID, Sales amount, and Customer ID; Customer data with Customer ID, Customer Name, and Region.

Cell	Value
A1	Order ID
B1	Sales
C1	Customer ID
A2	1001
B2	250
C2	C001
A3	1002
B3	450
C3	C002
A4	1003
B4	300
C4	C003
E1	Customer ID
F1	Customer Name
G1	Region
E2	C001
F2	Alice
G2	North
E3	C002
F3	Bob
G3	South
E4	C003
F4	Charlie
G4	East

Formula Trace

SUM([Sales]) by blending Sales data and Customer data on Customer ID

Step 1: Identify common field to blend: Customer ID

Step 2: Match Customer IDs from Sales data to Customer data

Step 3: Aggregate Sales by Customer ID

Step 4: Blend aggregated Sales with Customer data on Customer ID

Step 5: Calculate total Sales across all customers

Cell Reference Map

    A       B       C           E       F           G
1 |Order ID| Sales |Customer ID|Customer ID|Customer Name|Region
2 | 1001   |  250  |   C001    |   C001    |   Alice    | North
3 | 1002   |  450  |   C002    |   C002    |    Bob     | South
4 | 1003   |  300  |   C003    |   C003    |  Charlie   | East

Arrows:
B2,B3,B4 (Sales) linked to C2,C3,C4 (Customer ID) matched with E2,E3,E4 (Customer ID) to blend data.

Sales data columns A-C and Customer data columns E-G are linked by Customer ID to blend sales with customer details.

Result

    Customer ID | Customer Name | Region | Total Sales
1 |    C001     |    Alice     | North  |    250
2 |    C002     |     Bob      | South  |    450
3 |    C003     |   Charlie    | East   |    300

Total Sales across all customers: 1000

The blended data shows each customer with their region and total sales. The total sales sum is 1000.

Sheet Trace Quiz - 3 Questions

What is the common field used to blend the two data sources?

A Sales

B Order ID

C Customer ID

D Region

Key Result

Blend data sources by matching on a common key field and aggregate measures accordingly.

Practice

1. What is the main purpose of blending data sources in Tableau?

easy

A. To create a single table by merging all data sources permanently

B. To combine data from different sources using common fields without merging tables

C. To replace the primary data source with a secondary one

D. To export data from Tableau to external databases

Solution

1. Step 1: Understand blending concept

   Blending connects data from different sources using common fields without merging them permanently.

2. Step 2: Compare options

   To combine data from different sources using common fields without merging tables correctly describes blending. Options A, C, and D describe other unrelated actions.

3. Final Answer:

   To combine data from different sources using common fields without merging tables -> Option B

4. Quick Check:

   Blending = combine without merging [OK]

Hint: Blending links data without merging tables [OK]

Common Mistakes:

• Confusing blending with joining or merging tables
• Thinking blending replaces the primary source
• Assuming blending exports data

2. Which of the following is the correct way to identify the linking field in Tableau data blending?

easy

A. The field with a red cross in the primary data source

B. The field with a blue checkmark in the secondary data source

C. The field with a green plus sign in the primary data source

D. The field with an orange chain link icon in the secondary data source

Solution

1. Step 1: Recognize linking field icon

   In Tableau, linking fields in the secondary data source show an orange chain link icon.

2. Step 2: Match options to icons

   The field with an orange chain link icon in the secondary data source correctly identifies the orange chain link icon as the linking field. Other options describe incorrect icons or colors.

3. Final Answer:

   The field with an orange chain link icon in the secondary data source -> Option D

4. Quick Check:

   Linking field = orange chain link icon [OK]

Hint: Look for orange chain link icon for linking fields [OK]

Common Mistakes:

• Confusing linking field icon with checkmarks or plus signs
• Looking for icons in the primary instead of secondary source
• Ignoring icon colors

3. Given two data sources: Primary with fields OrderID, Sales and Secondary with fields OrderID, CustomerName. If you blend on OrderID and create a view showing Sales and CustomerName, what will happen if an OrderID exists only in the secondary source?

medium

A. The view will exclude that OrderID because it is missing in the primary source

B. The view will show Sales as null and CustomerName for that OrderID

C. The view will show Sales and CustomerName as null

D. The view will cause an error and not display

Solution

1. Step 1: Understand primary source control

   In blending, the primary source controls the rows shown. If an OrderID is missing in primary, it won't appear.

2. Step 2: Analyze missing OrderID in primary

   Since the OrderID exists only in secondary, it will be excluded from the view.

3. Final Answer:

   The view will exclude that OrderID because it is missing in the primary source -> Option A

4. Quick Check:

   Primary source controls rows = missing keys excluded [OK]

Hint: Primary source controls rows shown in blending [OK]

Common Mistakes:

• Expecting secondary-only keys to appear in the view
• Thinking null values appear for missing primary keys
• Assuming blending causes errors on missing keys

4. You blended two data sources on CustomerID. However, the secondary data source fields show Null values in your view. What is the most likely cause?

medium

A. You forgot to refresh the data sources

B. The primary data source is missing the CustomerID field

C. The linking field CustomerID has mismatched data types between sources

D. The secondary data source is set as primary by mistake

Solution

1. Step 1: Check linking field compatibility

   Blending requires linking fields to have matching data types to join correctly.

2. Step 2: Identify cause of nulls

   If data types differ, Tableau cannot match keys, causing nulls in secondary fields.

3. Final Answer:

   The linking field CustomerID has mismatched data types between sources -> Option C

4. Quick Check:

   Matching data types needed for linking fields [OK]

Hint: Check data types of linking fields if nulls appear [OK]

Common Mistakes:

• Assuming missing fields cause nulls instead of mismatched types
• Confusing primary and secondary source roles
• Ignoring need to refresh data

5. You have two data sources: SalesData (Primary) with OrderID, SalesAmount and CustomerData (Secondary) with CustomerID, OrderID, Region. You want to create a view showing total sales by region. How should you blend and aggregate the data correctly?

hard

A. Blend on OrderID, use Region from secondary, and create a calculated field summing SalesAmount grouped by Region

B. Blend on CustomerID, use Region from secondary, and sum SalesAmount without grouping

C. Join the two sources on OrderID instead of blending, then sum SalesAmount by Region

D. Blend on Region, then sum SalesAmount grouped by OrderID

Solution

1. Step 1: Identify correct linking field

   OrderID exists in both sources and links sales to customer region.

2. Step 2: Blend on OrderID and aggregate

   Blend on OrderID, use Region from secondary, then sum SalesAmount grouped by Region for total sales by region.

3. Final Answer:

   Blend on OrderID, use Region from secondary, and create a calculated field summing SalesAmount grouped by Region -> Option A

4. Quick Check:

   Blend on OrderID + sum Sales by Region [OK]

Hint: Blend on common key, aggregate sales by region [OK]

Common Mistakes:

• Blending on wrong field like CustomerID or Region
• Not grouping sales by region
• Confusing blending with joining