SCD DepthQuick Decisionbeginner5 min

When not to Type 2

Recognize the Type 1 trap when only current state is ever queried.

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Concept

slowly-changing-dimensions

The primary modeling idea this problem reinforces.

Requirements

Business needs the model must satisfy.

Read the concept guide: Slowly changing dimensions: Type 2

Scenario

People operations maintains an employee directory used only to route current approvals and show current managers. They explicitly do not report historical manager assignments from this table.

Why this matters

SCD work is not maximally historical by default. Over-versioning a current-only directory adds operational cost without improving the business workflow.

Requirements

Pick the SCD strategy for current employee directory attributes.
Explain what reporting requirement would have changed the answer.

What success looks like

The answer chooses Type 1 overwrite for the current-state directory.
The rationale names Type 2 as unnecessary unless historical manager assignment reporting is required.

Hints

Ask whether anyone needs to ask what the value used to be.
Changing attributes do not automatically require Type 2 history.

Common pitfalls

Reflexively choosing Type 2 because the attribute can change.
Ignoring the stated current-only workflow.
Adding version rows that no downstream metric or process will query.

Reference approaches

These are valid approaches, not one absolute answer.

Type 1 overwrite for current-only attributes

Overwrite current employee-directory attributes when historical values are not analytically required. A Kimball Type 1 slowly changing dimension.

Optimizes for

• Simple current-state lookup
• Lower row churn
• Operational clarity

Trade-offs

• Cannot reconstruct prior manager assignments from this table
• Would need Type 2 or an assignment fact if historical reporting becomes required

In this set

Problem 1 of 6 in SCD Depth.

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Which SCD strategy best fits this employee directory requirement?Use Type 1 overwrite for current employee attributes.Create a new Type 2 employee row for every manager change.Add many previous-manager columns for every prior manager.

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