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Pivot with CASE

Pivot using CASE and aggregates.

Pivot with CASE

You pivot with CASE and SUM. Each category becomes a column.

SELECT
  SUM(CASE WHEN category = 'Kitap' THEN amount ELSE 0 END) AS Kitap,
  SUM(CASE WHEN category = 'Elektronik' THEN amount ELSE 0 END) AS Elektronik
FROM sales;

Two columns for two categories.

SUM(CASE WHEN category = 'Kitap' THEN amount ELSE 0 END) … is selected from sales.

Pivot with CASE — details

CASE produces values per category, SUM aggregates them. Each category is a separate column.

Writing ELSE 0 for non-matching rows matters; without ELSE the CASE returns NULL, and while SUM still works, functions like COUNT can give wrong results.

Practice Pivot with CASE

Produce a Book column with SUM(CASE WHEN category = 'Kitap' THEN amount ELSE 0 END).

Starter code

query.sql
-- pivot with case
SELECT
  SUM(

Sample solution

query.sql
SELECT
  SUM(CASE WHEN category = 'Kitap' THEN amount ELSE 0 END) AS Kitap,
  SUM(CASE WHEN category = 'Elektronik' THEN amount ELSE 0 END) AS Elektronik
FROM sales;

Expected output

Kitap
200

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 Add SUM

Question 
SELECT
  ____(CASE WHEN category = 'Kitap' THEN amount ELSE 0 END) AS Kitap
FROM sales;
Answer 
SELECT
  SUM(CASE WHEN category = 'Kitap' THEN amount ELSE 0 END) AS Kitap
FROM sales;

Explanation: CASE returns the amount only for matching rows and 0 otherwise; SUM adds them up into a column.

2 What is summed in a CASE pivot?

  • The CASE result Correct answer
  • All rows
  • An index
  • The column name

Explanation: The CASE result is summed with SUM.

3 Pivot with CASE: match the terms

Term Meaning
CASE condition
SUM sum
category column
pivot convert

All lessons in Advanced

1 CTE

  1. What is a CTE?
  2. Using WITH
  3. Multiple CTEs
  4. CTE vs subquery
  5. CTE with JOIN
  6. Summary - CTE

2 Recursive CTE

  1. What is a recursive CTE?
  2. Anchor and recursive parts
  3. Walk a hierarchy
  4. Tracking depth
  5. Stopping recursion
  6. Summary - Recursive CTE

3 Window functions

  1. What is a window function?
  2. ROW_NUMBER
  3. RANK and DENSE_RANK
  4. LAG and LEAD
  5. PARTITION BY
  6. Summary - Window functions

4 Project: Analytics report

  1. Analytics design
  2. CTE summary
  3. Top users with ROW_NUMBER
  4. Growth with LAG
  5. Final report

5 Pivot and unpivot

  1. What is pivot?
  2. Pivot with CASE
  3. FILTER clause
  4. Unpivot
  5. Dynamic pivot
  6. Summary - Pivot

6 Materialized view

  1. What is a materialized view?
  2. CREATE
  3. REFRESH
  4. View vs materialized view
  5. Index on materialized views
  6. Summary - Materialized view

7 Stored procedure

  1. What is a procedure?
  2. CREATE PROCEDURE
  3. Parameters
  4. CALL
  5. Control flow
  6. Summary - Stored procedure

8 Function

  1. What is a function?
  2. CREATE FUNCTION
  3. RETURN
  4. Calling a function
  5. Function vs procedure
  6. Summary - Function

9 Trigger

  1. What is a trigger?
  2. BEFORE and AFTER
  3. INSERT trigger
  4. UPDATE trigger
  5. Write an audit trigger
  6. Summary - Trigger

10 Transaction isolation

  1. What is isolation?
  2. READ UNCOMMITTED
  3. READ COMMITTED
  4. REPEATABLE READ
  5. SERIALIZABLE
  6. Summary - Isolation

11 Locking

  1. What is a lock?
  2. Shared and exclusive locks
  3. Deadlock
  4. SELECT FOR UPDATE
  5. Lock timeout
  6. Summary - Locking

12 Query optimization

  1. What is EXPLAIN?
  2. Seq scan vs index scan
  3. Cost
  4. Sargable
  5. N+1 problem
  6. Summary - Optimization

13 Partitioning

  1. What is partitioning?
  2. Range partition
  3. List partition
  4. Hash partition
  5. Partition pruning
  6. Summary - Partitioning

14 Advanced final

  1. Hierarchy report
  2. Window analysis
  3. Procedure and trigger
  4. Optimization