LOD vs table calculations in Tableau - Quick Revision & Key Differences

Recall & Review

beginner

What does LOD stand for in Tableau?

LOD stands for Level of Detail. It lets you control the granularity of data calculations independently from the view.

intermediate

How do table calculations differ from LOD expressions?

Table calculations compute results based on the data already in the view, while LOD expressions compute results at a specified data granularity before the view is built.

beginner

Name one use case for LOD expressions.

Calculating sales per customer regardless of the current view filters or dimensions shown.

intermediate

What is a key limitation of table calculations?

They only work on the data visible in the current view and cannot access data outside the view's scope.

intermediate

Which calculation type is processed first: LOD or table calculations?

LOD calculations are processed before table calculations. LOD fixes data granularity early, then table calculations work on the result.

Which Tableau calculation can ignore the dimensions in the current view?

A Table calculations

B Aggregations in the view

C Quick table calculations

D LOD expressions

LOD expressions can fix the level of detail independently of the view's dimensions.

Table calculations in Tableau operate on:

A The raw data source

B Data after aggregation and filtering in the view

C Data before any filters

D Only calculated fields

Table calculations work on the data already aggregated and filtered in the view.

Which calculation type would you use to calculate the total sales per region regardless of the current filters?

A LOD expression

B Table calculation

C Quick filter

D Parameter

LOD expressions can fix calculations at a specific level, ignoring filters.

When are LOD calculations processed in Tableau's order of operations?

A After table calculations

B At the same time as table calculations

C Before table calculations

D Only when using filters

LOD calculations are processed before table calculations.

Which of these is NOT true about table calculations?

A They can access data outside the current view

B They depend on the layout of the view

C They are computed after aggregation

D They can be used for running totals

Table calculations cannot access data outside the current view.

Explain the main differences between LOD expressions and table calculations in Tableau.

Think about when and how each calculation type processes data.

Describe a scenario where you would prefer to use an LOD expression instead of a table calculation.

Consider when you want consistent results regardless of what is shown.

Practice

1. What is the main difference between LOD expressions and table calculations in Tableau?

easy

A. LOD expressions fix calculations at a specific data level, ignoring some filters, while table calculations work on the data shown in the current view.

B. LOD expressions only work on aggregated data, while table calculations only work on raw data.

C. LOD expressions are faster than table calculations in all cases.

D. Table calculations ignore filters, but LOD expressions depend on the table layout.

Solution

1. Step 1: Understand LOD expressions

   LOD expressions fix the calculation at a certain level of detail, ignoring some filters applied to the view.

2. Step 2: Understand table calculations

   Table calculations work on the data currently displayed in the view and depend on how the table is laid out.

3. Final Answer:

   LOD expressions fix calculations at a specific data level, ignoring some filters, while table calculations work on the data shown in the current view. -> Option A

4. Quick Check:

   LOD fixes level, table calculations depend on view [OK]

Hint: LOD fixes level, table calculations depend on view layout [OK]

Common Mistakes:

• Thinking table calculations ignore filters
• Believing LOD always works on raw data
• Assuming LOD is always faster

2. Which of the following is the correct syntax for a fixed LOD expression in Tableau to calculate total sales per region?

easy

A. { EXCLUDE [Region] : SUM([Sales]) }

B. { INCLUDE [Region] : SUM([Sales]) }

C. { FIXED [Region] : SUM([Sales]) }

D. SUM([Sales]) FIXED BY [Region]

Solution

1. Step 1: Recall fixed LOD syntax

   The fixed LOD syntax is { FIXED [Dimension] : Aggregation }.

2. Step 2: Match syntax to question

   { FIXED [Region] : SUM([Sales]) } matches the correct syntax for total sales per region.

3. Final Answer:

   { FIXED [Region] : SUM([Sales]) } -> Option C

4. Quick Check:

   Fixed LOD uses FIXED keyword and curly braces [OK]

Hint: Fixed LOD always starts with { FIXED ... } [OK]

Common Mistakes:

• Using INCLUDE or EXCLUDE instead of FIXED
• Missing curly braces
• Incorrect keyword order

3. Given a view showing sales by category and sub-category, what will the following LOD expression return?
{ FIXED [Category] : SUM([Sales]) }

medium

A. Total sales for each sub-category ignoring category

B. Total sales for each category repeated for all sub-categories within it

C. Total sales for the entire dataset ignoring category and sub-category

D. Running total of sales by sub-category

Solution

1. Step 1: Understand FIXED by Category

   The expression fixes sales at the category level, ignoring sub-category detail.

2. Step 2: Effect on sub-category rows

   Each sub-category row will show the total sales of its parent category, repeated.

3. Final Answer:

   Total sales for each category repeated for all sub-categories within it -> Option B

4. Quick Check:

   Fixed LOD repeats category total per sub-category [OK]

Hint: Fixed LOD repeats fixed level value for lower detail rows [OK]

Common Mistakes:

• Thinking it sums only sub-category sales
• Confusing FIXED with INCLUDE or EXCLUDE
• Assuming running total behavior

4. You created a table calculation for running total of sales but it shows incorrect results. Which of the following is the most likely cause?

medium

A. The filter is applied before the LOD calculation.

B. The LOD expression used is FIXED instead of INCLUDE.

C. The data source is missing a join condition.

D. The table calculation is not set to compute using the correct dimension.

Solution

1. Step 1: Understand table calculation behavior

   Table calculations depend on the table layout and the dimension used for computation.

2. Step 2: Identify common error

   If the running total is wrong, often the compute using dimension is set incorrectly.

3. Final Answer:

   The table calculation is not set to compute using the correct dimension. -> Option D

4. Quick Check:

   Table calcs need correct compute using dimension [OK]

Hint: Check 'compute using' dimension for table calculations [OK]

Common Mistakes:

• Confusing LOD and table calculation errors
• Blaming data joins for table calc issues
• Ignoring table layout impact

5. You want to show the percent of total sales by region in a view that filters by year. Which approach is best to ensure the percent always reflects all years, ignoring the year filter?

hard

A. Use a FIXED LOD expression to calculate total sales by region ignoring the year filter, then divide sales by this fixed total.

B. Use a table calculation for percent of total sales by region, which automatically ignores filters.

C. Apply the year filter after creating a table calculation for percent of total sales.

D. Use an INCLUDE LOD expression including year to calculate sales.

Solution

1. Step 1: Understand filter impact on calculations

   Table calculations and INCLUDE LOD respect filters, so year filter affects them.

2. Step 2: Use FIXED LOD to ignore year filter

   FIXED LOD can ignore filters like year, fixing total sales by region across all years.

3. Step 3: Calculate percent of total

   Divide sales by the fixed total sales to get percent ignoring year filter.

4. Final Answer:

   Use a FIXED LOD expression to calculate total sales by region ignoring the year filter, then divide sales by this fixed total. -> Option A

5. Quick Check:

   FIXED LOD ignores filters, perfect for fixed percent totals [OK]

Hint: Use FIXED LOD to ignore filters for fixed percent totals [OK]

Common Mistakes:

• Using table calculations that respect filters
• Using INCLUDE LOD which respects filters
• Applying filters after calculations incorrectly