How to use case function in sql

SQL CASE function performs different operations by comparing expression results. Its syntax is: WHEN expression THEN result1WHEN expression THEN result2...[ELSE default_result]END

Usage of CASE function in SQL

The CASE function is a powerful tool in SQL that is used to perform different operations based on the result of an expression. The syntax is as follows:

<code class="sql">CASE
  WHEN expression1 THEN result1
  WHEN expression2 THEN result2
  ...
  [ELSE default_result]
END</code>

Usage example

For example, to get an employee's salary range based on their department, you can use the CASE function:

<code class="sql">SELECT
  salary,
  CASE department
    WHEN 'Sales' THEN '25,000 - 50,000'
    WHEN 'Engineering' THEN '35,000 - 75,000'
    WHEN 'Marketing' THEN '20,000 - 40,000'
    ELSE 'Unknown'
  END AS salary_range
FROM
  employees;</code>

This will return the following results:

Other Use Cases

• Verify data integrity: Verify whether the data meets certain conditions.
• Convert data format: Convert data from one format to another.
• Aggregate data: Group and summarize data according to different conditions.
• Complex query: Perform different operations according to different situations in complex queries.

Note:

The CASE statement can contain multiple WHEN clauses and an optional ELSE clause.
• The ELSE clause can be used to specify the default result when all WHEN clauses are not satisfied.
• CASE statements can be nested to create more complex conditions.

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