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Explain the use of CASE in SQL.

Parthiban Kannan
Updated on December 2, 2025

1 min read

The CASE statement in SQL is used to add conditional logic inside a query — it’s like an IF-THEN-ELSE structure. It lets us create new calculated columns or apply different logic based on certain conditions directly within a SQL query.

For example, suppose I have a table called Employees with a column Salary, and I want to classify employees based on their salary level. I can write:

🗃️
filename.sql 
SELECT 
   EmployeeName,
   Salary,
   CASE 
      WHEN Salary > 100000 THEN 'High'
      WHEN Salary BETWEEN 50000 AND 100000 THEN 'Medium'
      ELSE 'Low'
   END AS SalaryCategory
FROM Employees;

Here, the CASE statement checks each employee’s salary and assigns a label accordingly — High, Medium, or Low. This helps make reports more readable and meaningful without changing the underlying data.

I used this concept in a sales performance dashboard project. We had to group sales reps based on their target achievement percentage — for example, “Achieved,” “Below Target,” and “Outstanding.” Instead of creating multiple queries or temporary tables, a simple CASE statement inside the SELECT clause handled it neatly.

One challenge I faced was when nested CASE conditions became too complex. It made the query harder to read and debug. In such cases, I usually simplify it by using lookup tables or computed columns in the database instead.

A limitation of CASE is that it doesn’t support multiple outputs for one condition — it can only return a single value. If I need more dynamic transformations or multiple condition checks, I sometimes switch to using JOINs with mapping tables or handle that logic in the application layer.

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