The CASE WHEN statement is a powerful tool in Databricks for conditionally assigning values to a new column based on different conditions. It’s essentially a way to create custom logic within your SQL queries.

Here’s the basic syntax:

SELECT ...,
  CASE WHEN condition1 THEN result1
       WHEN condition2 THEN result2
       ...
       ELSE default_result
  END AS new_column_name
FROM your_table;

Breakdown:

• conditionN: This is a boolean expression that evaluates to true or false.
• resultN: The value assigned to the new column if the corresponding conditionN is true.
• default_result (optional): The value assigned if none of the conditions are true.
• new_column_name: The name you give to the new column containing the results of the logic.

Example:

Let’s say you have a table with a column “age” and want to create a new column “age_group” that categorizes people based on age. You can use CASE WHEN like this:

SELECT name, age,
  CASE WHEN age < 18 THEN 'Under 18'
       WHEN age >= 18 AND age < 65 THEN 'Adult'
       ELSE 'Senior'
  END AS age_group
FROM people_data;

This will create a new column “age_group” that assigns “Under 18” to people younger than 18, “Adult” to people between 18 and 64 (inclusive), and “Senior” to everyone else.

Benefits of using CASE WHEN:

• Improves code readability by replacing complex conditional logic with clear statements.
• Creates new columns with categorized or transformed data.
• Makes your queries more concise and easier to maintain.

Further Learning:

For more details and advanced usage of CASE WHEN in Databricks, you can refer to the official documentation: https://docs.databricks.com/en/sql/language-manual/functions/case.html