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Data Analysis & SQL · Practitioner lesson 13 of 19

Custom Category Buckets

Segment numerical data into business tiers like High, Medium, and Low with CASE WHEN.

Why this matters

Reports often need labels like High, Medium, and Low. CASE WHEN builds them inside the query, with no spreadsheet work.

Build Tiers in the Query

You do not need to sort numbers by hand in Excel. CASE WHEN builds labels like High and Medium right inside your query.

In real life: CASE WHEN is SQL's if-then. SQL tests each WHEN in order and uses the first one that is true.

Always Add an ELSE

Rows that match no WHEN become blank (NULL) if you leave out ELSE. Add a fallback, like ELSE 'Standard'.

In real life: A marking scheme that says A, B, or C but forgets the "fail" case leaves some pupils with no grade. ELSE makes sure every row gets a label.

End With AS and a Name

Finish with END AS order_tier. This gives the new column a clear name that others can read.

In real life: A column with no title is confusing. END AS order_tier is the title that tells the next person what the column means.

Your practice task

Segment orders into business tiers: mark amounts of 500 or more as 'High', amounts of 100 or more as 'Medium', and everything else as 'Standard', labeled AS order_tier.

How to do it

  1. Write down the three tiers and their limits.
  2. Check the biggest limit first, then the next.
  3. Decide the label for everything left over.
  4. Name the new column as the brief says, then press Run proof.

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Quick reference: Conditional Tier Bucket

The standard SQL technique for customer segmentation and cohort analysis.

SELECT customer_id,
  CASE
    WHEN spend >= 1000 THEN 'VIP'
    WHEN spend >= 250 THEN 'Regular'
    ELSE 'Occasional'
  END AS customer_tier
FROM customer_stats;

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